Recombinant Anaeromyxobacter dehalogenans Undecaprenyl-diphosphatase (uppP)
Description
Biochemical Identity and Classification
Undecaprenyl-diphosphatase (uppP) from Anaeromyxobacter dehalogenans is classified as a hydrolase enzyme (EC 3.6.1.27) that specifically targets the pyrophosphate bonds in undecaprenyl pyrophosphate. This membrane-bound enzyme is also known as bacitracin resistance protein due to its role in conferring resistance to the antibiotic bacitracin, which otherwise binds to undecaprenyl pyrophosphate and disrupts cell wall synthesis . The enzyme belongs to a conserved family of phosphatases that are integral to bacterial membrane systems and cellular envelope formation. Unlike other phosphatases involved in various metabolic pathways, uppP has evolved specificity for the lipid carrier crucial to cell wall formation, making it an essential enzyme for bacterial survival and integrity .
The uppP protein represents a significant point of intervention in bacterial physiology, as it catalyzes a rate-limiting step in peptidoglycan synthesis. This strategic position in bacterial metabolism has attracted considerable attention from researchers seeking to understand bacterial cell wall biosynthesis and develop novel antimicrobial strategies. The recombinant expression of this protein has facilitated detailed investigations that would otherwise be challenging with native membrane proteins extracted directly from bacterial sources.
Biological Significance in Bacterial Cell Wall Synthesis
Undecaprenyl-diphosphatase occupies a critical junction in the lipid carrier cycle essential for bacterial cell wall synthesis. The enzyme catalyzes the dephosphorylation of undecaprenyl pyrophosphate (C55-PP) to produce undecaprenyl phosphate (C55-P), which serves as the lipid carrier for peptidoglycan precursors across the cytoplasmic membrane . This process is part of both the de novo synthesis pathway and the recycling pathway of the lipid carrier. The recycling pathway is particularly important for bacteria, as it allows for the efficient reuse of the limited pool of undecaprenyl carriers in the cell .
Research has suggested distinct spatial orientations for different phosphatases involved in undecaprenyl pyrophosphate metabolism. While some evidence suggests uppP may participate in the de novo synthesis pathway at the cytoplasmic site, structural analysis indicates that its active site may actually be oriented toward the periplasmic space, challenging previous assumptions about its exclusive cytoplasmic role . This topological orientation has significant implications for understanding the complete cycle of peptidoglycan synthesis and the strategic targeting of these pathways for antimicrobial development.
Protein Architecture and Domains
Recombinant A. dehalogenans uppP is a full-length protein consisting of 292 amino acids with a complex membrane-spanning architecture . Analysis of the protein sequence reveals multiple transmembrane domains that anchor the protein within the bacterial membrane, positioning the catalytic domains appropriately for interaction with the membrane-embedded substrate. The complete amino acid sequence of the recombinant protein has been determined as: "MSLVSAALFGLLQALTEFLPVSSTAHLLVFGELLGHSLDDRRFRAFVTIIQAGTTLAVLVYFRADIARLVAAAARGLARGRPFGTPEARLGWYIVLGTVPAALAGKLLEHRIEALGNWVIAGSLVALGLVLLAAERLASHRRRVEDVGAGDALLIGVAQALALVPGSSRSGTTITGGMLLGFTREAAARFSFLLSVPITLAAGAYKLWSTVPDLRGEAAWTVATVVGTVVSAVAGYLVIDWLLAWLRTRTTYVFVVWRLAAGAAIAALILSGVLPAGAEAPPPPPPALHAAP" .
The structural analysis of uppP reveals two consensus regions that are highly conserved across bacterial species, containing glutamate-rich (E/Q)XXXE motifs and PGXSRSXXT motifs . These conserved regions are believed to form the active site of the enzyme and are localized near the aqueous interface of the protein. Importantly, three-dimensional modeling suggests that both of these consensus regions are oriented toward the periplasmic side of the plasma membrane, providing strong evidence that the biological function of uppP occurs on the outer side of the plasma membrane rather than the cytoplasmic side as previously thought .
Active Site Composition and Functional Motifs
The active site of uppP has been characterized through a combination of computational modeling, molecular dynamics simulations, and site-directed mutagenesis studies . Two critical consensus motifs have been identified as essential components of the enzyme's active site: the (E/Q)XXXE motif and the PGXSRSXXT motif . The glutamate residues in the (E/Q)XXXE motif are proposed to be involved in the coordination of divalent metal ions that are required for catalytic activity, while the PGXSRSXXT motif appears to form a structural P-loop that interacts with the phosphate groups of the substrate.
Additionally, a conserved histidine residue (His-30 in E. coli uppP) has been found to be in close proximity to the pyrophosphate moiety of the substrate in structural models . Mutation studies have demonstrated that replacement of this histidine with alanine (H30A) severely impairs enzyme activity, highlighting its critical role in catalysis. Similarly, mutation of an arginine residue (Arg-174 in E. coli) that establishes hydrogen bonds with the hydroxyl group of the pyrophosphate moiety results in complete loss of activity, further delineating the key residues involved in substrate recognition and catalysis .
Expression Systems and Purification Strategies
Recombinant A. dehalogenans uppP has been successfully expressed in Escherichia coli expression systems, providing a reliable source of the protein for structural and functional studies . The recombinant expression typically involves the addition of affinity tags, such as polyhistidine (His) tags, to facilitate purification of the membrane protein . The His-tagged recombinant protein can be efficiently purified using immobilized metal affinity chromatography (IMAC), allowing for the isolation of high-purity protein suitable for biochemical and structural analyses.
The expression of full-length uppP (amino acids 1-292) ensures that all structural domains and functional motifs are present in the recombinant protein . This is particularly important for membrane proteins like uppP, where truncation can significantly impact folding, membrane insertion, and ultimately function. The successful expression of recombinant uppP represents a significant achievement given the challenges typically associated with the expression and purification of integral membrane proteins, which often suffer from poor expression, misfolding, or aggregation when expressed in heterologous systems.
Enzymatic Reaction and Substrate Specificity
Undecaprenyl-diphosphatase catalyzes the hydrolysis of undecaprenyl pyrophosphate (UPP) to undecaprenyl phosphate (UP), releasing inorganic phosphate in the process . This reaction is critical for the regeneration of the lipid carrier that transports peptidoglycan precursors across the cytoplasmic membrane during bacterial cell wall synthesis. The enzyme exhibits high specificity for its natural substrate, undecaprenyl pyrophosphate, which is a C55 isoprenoid lipid carrier essential for bacterial cell wall biosynthesis .
The catalytic mechanism involves the coordination of divalent metal ions, typically Mg²⁺ or Mn²⁺, by the conserved glutamate residues in the (E/Q)XXXE motif . These metal ions facilitate the nucleophilic attack on the phosphoanhydride bond of the pyrophosphate moiety. The conserved histidine residue likely acts as a general base, activating a water molecule for nucleophilic attack, while the arginine residue helps position the substrate through hydrogen bonding interactions with the pyrophosphate group .
Regulation and Cellular Localization
The regulation of uppP activity is intricately linked to bacterial cell wall synthesis rates and cellular demands for peptidoglycan precursors. While the detailed regulatory mechanisms controlling uppP expression and activity are not fully elucidated, it is clear that the enzyme plays a crucial role in both the de novo synthesis and recycling pathways of undecaprenyl phosphate . The enzyme's orientation within the membrane is particularly significant, as it determines which pool of undecaprenyl pyrophosphate (cytoplasmic or periplasmic) it can access.
As mentioned earlier, topological analyses and structural modeling suggest that the active site of uppP is oriented toward the periplasmic space, challenging previous assumptions about its exclusive role in cytoplasmic de novo synthesis . This periplasmic orientation suggests that uppP may be more involved in the recycling pathway than previously thought, working in concert with other phosphatases (PgpB, YbjG, and LpxT) that are known to function in the periplasmic recycling of undecaprenyl pyrophosphate . This spatial organization allows for efficient recycling of the limited pool of lipid carriers, which is critical for maintaining the integrity of the bacterial cell wall during growth and division.
Mutagenesis Studies and Functional Implications
Extensive mutagenesis studies have been conducted to identify key residues involved in the catalytic activity of uppP . These studies have primarily focused on the conserved motifs and residues that are predicted to form the enzyme's active site. Site-directed mutagenesis of residues in the (E/Q)XXXE motif confirms their essential role in metal ion coordination and catalysis, with mutations in these positions resulting in significant reduction or complete loss of enzymatic activity .
Similarly, mutations in the conserved histidine residue (H30A in E. coli) and arginine residue (R174A in E. coli) lead to severely impaired enzyme activity, highlighting their critical roles in the catalytic mechanism . These mutagenesis studies, combined with structural modeling, have provided valuable insights into the structure-function relationships of uppP and have helped elucidate the molecular basis of its catalytic activity. The findings from these studies not only advance our understanding of bacterial cell wall biosynthesis but also provide potential targets for the development of novel antibiotics that could inhibit this essential process.
Comparative Analysis with Related Enzymes
Undecaprenyl-diphosphatase belongs to a larger family of phosphatases involved in various aspects of bacterial metabolism. Comparative analysis with related enzymes, such as other undecaprenyl pyrophosphate phosphatases (PgpB, YbjG, and LpxT), has revealed both shared features and unique characteristics of uppP . All these enzymes catalyze the dephosphorylation of undecaprenyl pyrophosphate, but they may differ in their substrate specificity, regulatory mechanisms, and cellular localization.
Interestingly, while undecaprenyl diphosphate synthase (UPS), which synthesizes undecaprenyl pyrophosphate, belongs to the family of cis-prenyl chain elongating enzymes, its structure is distinctly different from the "isoprenoid synthase fold" that is common to many enzymes involved in isoprenoid biosynthesis . This structural divergence highlights the specialized nature of the enzymes involved in undecaprenyl metabolism and the unique evolutionary adaptations that have occurred in this pathway. The detailed characterization of uppP and related enzymes contributes to our broader understanding of bacterial cell envelope biogenesis and provides a foundation for targeted antimicrobial development.
Potential as Antimicrobial Target
Given its essential role in bacterial cell wall biosynthesis, uppP represents a promising target for antimicrobial development . The bacterial cell wall is a critical structure that provides mechanical strength and protection against osmotic lysis, and its synthesis is the target of many clinically important antibiotics, including β-lactams, glycopeptides, and bacitracin. By targeting uppP, it may be possible to develop novel antibiotics that disrupt bacterial cell wall synthesis through a mechanism distinct from existing antibiotics, potentially circumventing established resistance mechanisms.
The structural and functional characterization of recombinant A. dehalogenans uppP provides valuable information for structure-based drug design efforts aimed at developing specific inhibitors of this enzyme . The identification of the active site residues and the elucidation of the catalytic mechanism offer specific molecular targets for rational drug design. Furthermore, the distinct structure of uppP compared to human phosphatases provides an opportunity for developing selective inhibitors with minimal off-target effects in human cells, which is a critical consideration in antibiotic development.
Research Tools and Biotechnological Applications
Recombinant A. dehalogenans uppP serves as a valuable research tool for studying bacterial cell wall biosynthesis and the lipid carrier cycle . The availability of purified, well-characterized recombinant protein facilitates biochemical assays, inhibitor screening, and structural studies that would be challenging with the native membrane-bound enzyme. Additionally, the recombinant protein can be used in the development of high-throughput screening assays for identifying novel inhibitors of bacterial cell wall synthesis.
Beyond its utility in basic research and drug discovery, recombinant uppP may have potential applications in biotechnology. For instance, it could be used in enzymatic synthesis of lipid-linked oligosaccharides or other glycoconjugates that require undecaprenyl phosphate as a carrier. The detailed understanding of uppP structure and function also contributes to our knowledge of membrane protein biology and the mechanisms of phosphatase enzymes, which has broader implications for protein engineering and synthetic biology applications.
Product Specs
Please note: We prioritize shipping the format currently in stock. However, if you have specific requirements for the format, please specify them in your order. We will prepare the product according to your request.
Note: All our proteins are shipped with standard blue ice packs by default. If you require dry ice shipping, please contact us in advance, as additional fees will apply.
Generally, the shelf life of the liquid form is 6 months at -20°C/-80°C. The shelf life of the lyophilized form is 12 months at -20°C/-80°C.
Target Background
KEGG: acp:A2cp1_0175
Q&A
What is the biological function of Undecaprenyl-diphosphatase (uppP) in bacterial cell wall synthesis?
Undecaprenyl-diphosphatase (uppP) catalyzes the dephosphorylation of undecaprenyl pyrophosphate (UPP, C55-PP) to undecaprenyl phosphate (C55-P), which serves as a critical lipid carrier in bacterial cell wall biosynthesis. This enzymatic conversion is essential for peptidoglycan synthesis as well as for the formation of other cell wall components including wall teichoic acids, lipopolysaccharides, and O-antigens. The dephosphorylation step enables the recycling of the lipid carrier, making it available for subsequent rounds of cell wall precursor transport across the cytoplasmic membrane. The enzyme is also known as Bacitracin resistance protein because it contributes to bacterial resistance against this antibiotic by modifying its target molecule .
What structural characteristics define A. dehalogenans uppP?
A. dehalogenans uppP (Uniprot accession Q2IMA5) is a 292-amino acid protein with several transmembrane domains consistent with its function at the bacterial membrane interface. Its amino acid sequence reveals a hydrophobic profile typical of membrane-associated enzymes with alternating hydrophobic and hydrophilic regions. The protein contains conserved catalytic motifs characteristic of the undecaprenyl pyrophosphate phosphatase family, including regions involved in coordination of divalent metal ions essential for its phosphatase activity. The ordered locus name for uppP in A. dehalogenans strain 2CP-C is Adeh_0157, and the encoded protein functions as an EC 3.6.1.27 class enzyme (phosphoanhydride hydrolase) .
How does uppP differ from Undecaprenyl pyrophosphate synthase (UppS/UPPS)?
While functionally related in the same pathway, uppP and UPPS catalyze different reactions in bacterial cell wall biosynthesis. UPPS is a cis-prenyltransferase that synthesizes undecaprenyl pyrophosphate (UPP) by catalyzing the condensation of farnesyl diphosphate with eight molecules of isopentenyl diphosphate. In contrast, uppP acts downstream by dephosphorylating the UPP produced by UPPS to generate undecaprenyl phosphate (C55-P). Both enzymes are essential for bacterial peptidoglycan synthesis but represent distinct enzymatic steps and potential antibiotic targets. Inhibiting either enzyme disrupts cell wall formation, but through different mechanisms, which has implications for developing targeted antimicrobial strategies .
What expression systems are suitable for producing recombinant A. dehalogenans uppP?
Recombinant A. dehalogenans uppP can be expressed using several heterologous systems, with E. coli being the most common platform. For optimal expression, codon optimization based on the host organism is recommended, particularly given the GC content differences between A. dehalogenans and common expression hosts. Expression vectors containing T7 or similar strong inducible promoters, combined with appropriate fusion tags (His6, GST, or MBP) facilitate both expression and subsequent purification. Because uppP is a membrane-associated enzyme, specialized expression systems that enhance membrane protein production may be necessary, such as C41(DE3) or C43(DE3) E. coli strains designed for toxic membrane protein expression. Temperature optimization (typically 16-25°C for membrane proteins) and induction conditions require careful calibration to balance protein yield with proper folding .
What methodological approaches are most effective for assessing uppP enzymatic activity?
Assessment of uppP enzymatic activity requires specialized approaches due to its membrane-associated nature and the lipid-based substrate. A comprehensive activity assay typically combines multiple methods:
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Phosphate release assay: Quantification of inorganic phosphate released during the dephosphorylation reaction using colorimetric methods (malachite green or molybdate-based).
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HPLC-based substrate conversion: Direct monitoring of UPP consumption and C55-P production using reverse-phase HPLC with appropriate lipid detection methods.
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Radiometric assays: Using 32P-labeled UPP substrate to track dephosphorylation through thin-layer chromatography or scintillation counting.
For meaningful enzymatic characterization, activity assays should be conducted within appropriate detergent micelles or reconstituted membrane environments to maintain enzyme conformation and function. Reaction conditions should be systematically optimized for pH (typically 6.5-8.0), divalent metal ion concentration (usually Mg2+ or Mn2+), and ionic strength to determine kinetic parameters (Km, Vmax) accurately. Controls using known uppP inhibitors like bacitracin can help validate assay specificity .
How can researchers effectively differentiate between the activities of uppP and other phosphatases in complex bacterial systems?
Differentiating uppP activity from other phosphatases in bacterial systems requires multi-faceted approaches:
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Substrate specificity analysis: Compare dephosphorylation rates of UPP versus other phosphorylated substrates. Authentic uppP shows strong preference for UPP over generic phosphatase substrates like p-nitrophenyl phosphate.
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Inhibitor profiling: Utilize differential sensitivity to inhibitors. For example, bacitracin specifically inhibits UPP-related pathways, while phosphatase inhibitors like sodium orthovanadate affect a broader range of phosphatases.
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Genetic approaches: Construct and characterize uppP knockout mutants alongside complementation studies with the recombinant enzyme to confirm phenotypic effects.
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Activity under native-like conditions: Assess activity in membrane fractions versus soluble fractions, as uppP activity should predominantly associate with membrane components.
Developing a comprehensive biochemical profile through these approaches enables researchers to attribute observed enzymatic activities specifically to uppP rather than to other phosphatases that may be present in the experimental system .
What structural and functional properties of A. dehalogenans uppP contribute to its potential role in bioremediation applications?
A. dehalogenans uppP's potential contributions to bioremediation applications stem from several structural and functional properties:
Understanding these properties has practical implications for enhancing bioremediation strategies, as manipulation of cell wall synthesis pathways could potentially improve bacterial survival and performance in contaminated environments .
How does the function of uppP relate to antibiotic resistance mechanisms?
The relationship between uppP function and antibiotic resistance is multifaceted and mechanistically significant:
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Direct resistance mechanism: As a bacitracin resistance protein, uppP directly counteracts this antibiotic's mode of action. Bacitracin forms complexes with undecaprenyl pyrophosphate, preventing its dephosphorylation; elevated uppP activity can overcome this inhibition by increasing the dephosphorylation rate.
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Cell wall integrity maintenance: By ensuring continuous recycling of the lipid carrier, uppP supports robust cell wall synthesis even under antibiotic stress targeting other steps in peptidoglycan assembly.
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Collateral effects on other antibiotics: Alterations in uppP expression can have unexpected effects on susceptibility to other cell wall-targeting antibiotics. For instance, reduced expression of the related enzyme UppS in Bacillus subtilis conferred increased resistance to vancomycin, fosfomycin, and D-cycloserine, while simultaneously increasing susceptibility to β-lactams .
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Regulatory interactions: uppP activity influences the expression of cell wall stress response regulons (such as σM in B. subtilis), which can provide broader antibiotic resistance phenotypes through coordinated expression of multiple resistance determinants .
These complex interactions highlight why targeting cell wall lipid carrier metabolism represents a promising strategy for novel antibacterial development or for restoring sensitivity to existing antibiotics .
What purification strategies are most effective for obtaining active recombinant A. dehalogenans uppP?
Purification of active recombinant A. dehalogenans uppP requires specialized approaches due to its membrane-associated nature:
Table 1. Comparative Purification Strategies for Recombinant uppP
| Strategy | Advantages | Limitations | Recommended Conditions |
|---|---|---|---|
| Detergent Extraction | Maintains native-like lipid environment | Detergent may interfere with activity assays | 1-2% n-Dodecyl β-D-maltoside, 4°C extraction |
| Affinity Chromatography | High purity in single step | Tag may affect activity | His6-tag with IMAC, low imidazole washes |
| Size Exclusion | Removes aggregates, determines oligomeric state | Dilution of protein | Buffer containing 0.05% DDM, flow rate <0.5 ml/min |
| Ion Exchange | Separates charge variants | Salt concentration may destabilize protein | Gradual salt gradient (50-500 mM NaCl) |
| Reconstitution in Nanodiscs | Native-like bilayer environment | Complex preparation | MSP1D1:lipid:protein ratio optimization |
Critical considerations include maintaining a suitable detergent concentration throughout purification, preventing protein aggregation, and verifying that the purified enzyme retains catalytic activity. Final preparations should be assessed for purity by SDS-PAGE and for activity using phosphatase assays specific for the natural substrate. Storage conditions should include 50% glycerol in a Tris-based buffer at -20°C for short-term storage or -80°C for extended periods, with avoidance of repeated freeze-thaw cycles .
What experimental approaches can detect uppP-protein interactions in bacterial systems?
Detecting uppP-protein interactions requires techniques suitable for membrane-associated proteins:
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Bacterial two-hybrid systems: Modified for membrane protein analysis, these genetic approaches can identify protein-protein interactions in vivo, though sensitivity may be limited for membrane proteins.
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Co-immunoprecipitation with membrane solubilization: Using epitope-tagged uppP and carefully optimized detergent conditions to maintain native interactions during solubilization, followed by affinity purification and mass spectrometry identification of binding partners.
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Cross-linking coupled with mass spectrometry: Chemical cross-linking agents can capture transient interactions before solubilization, with subsequent MS analysis to identify proximity-based interactions.
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Fluorescence resonance energy transfer (FRET): Tagged versions of uppP and potential partners can be monitored for energy transfer indicative of close association in membrane environments.
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Split fluorescent protein complementation: Fragments of fluorescent proteins fused to uppP and potential interacting partners can reconstitute fluorescence when brought into proximity by protein interaction.
Each approach has specific strengths and limitations, and combining multiple methods provides the most robust evidence for genuine protein-protein interactions. Control experiments with known non-interacting membrane proteins are essential to establish specificity .
How can researchers accurately quantify A. dehalogenans uppP expression levels in environmental samples?
Quantifying A. dehalogenans uppP expression in environmental samples requires sensitive techniques that can detect the target gene amidst complex microbial communities:
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Quantitative real-time PCR (qPCR): Design of uppP-specific primers and TaqMan probes that distinguish A. dehalogenans uppP from related sequences in other organisms enables quantification of gene copy numbers. Multiplex qPCR approaches similar to those used for 16S rRNA genes can simultaneously track multiple targets.
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Reverse transcription qPCR (RT-qPCR): By targeting mRNA rather than genomic DNA, this approach measures actual gene expression levels rather than merely detecting gene presence.
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Droplet digital PCR (ddPCR): This technique provides absolute quantification without standard curves and offers higher precision for low-abundance targets typically found in environmental samples.
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Meta-transcriptomics: RNA sequencing of environmental samples followed by bioinformatic analysis can reveal uppP expression in the context of the entire community transcriptome.
For environmental studies, proper sample preservation (immediate flash freezing or RNAlater treatment), efficient nucleic acid extraction from soil or sediment matrices, and rigorous controls to account for PCR inhibitors are crucial for reliable results. Reference genes with stable expression should be included for normalization across samples with varying biomass .
What considerations are important when designing site-directed mutagenesis experiments for A. dehalogenans uppP?
Site-directed mutagenesis of A. dehalogenans uppP requires careful planning considering both the protein's membrane-associated nature and its catalytic function:
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Target residue selection: Prioritize conserved residues identified through multiple sequence alignments of bacterial undecaprenyl pyrophosphatases. Focus on residues in predicted catalytic sites, substrate binding regions, and membrane interaction domains.
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Mutation type selection: Consider conservative mutations to probe specific chemical properties (e.g., D→E to maintain charge but alter side chain length) versus non-conservative mutations for more dramatic functional changes.
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Structural context: Although a crystal structure may not be available, homology modeling based on related phosphatases can guide mutation design by predicting structural consequences.
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Functional validation plan: Design a comprehensive panel of assays to assess mutant effects, including protein expression levels, membrane localization, enzymatic activity, and physiological consequences in complementation studies.
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Controls: Include both positive controls (wild-type enzyme) and negative controls (catalytically inactive mutants targeting established active site residues).
When expressing mutants, careful calibration of induction conditions may be necessary, as mutations can sometimes affect protein stability or toxicity to the expression host. Parallel characterization of multiple mutants enables the development of a structure-function relationship map of the enzyme's key features .
How is A. dehalogenans uppP involved in uranium bioremediation processes?
A. dehalogenans uppP's role in uranium bioremediation processes is primarily indirect but potentially significant:
Understanding the role of uppP in maintaining cellular function under uranium stress could potentially inform strategies to enhance bioremediation efficiency through optimization of bacterial survival and activity .
What experimental approaches best demonstrate the relationship between uppP activity and antibiotic resistance?
The relationship between uppP activity and antibiotic resistance can be experimentally established through multiple complementary approaches:
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Gene expression modulation studies: Controlled overexpression or knockdown of uppP using inducible promoters or antisense RNA, followed by minimum inhibitory concentration (MIC) determination for various antibiotics. This approach directly correlates uppP expression levels with resistance phenotypes.
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Genetic reconstruction experiments: Introduction of uppP mutations (similar to the uppS1 mutation in B. subtilis) that affect translation efficiency, followed by assessment of antibiotic susceptibility profiles. This approach establishes causality between gene dosage and resistance .
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Antibiotic synergy assays: Testing combinations of uppP inhibitors with various cell wall-targeting antibiotics using checkerboard assays to identify synergistic, antagonistic, or indifferent interactions, revealing pathway-level interactions.
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Time-kill kinetics: Measuring bacterial killing rates under antibiotic exposure with varying levels of uppP activity to determine if the enzyme affects the rate of antibiotic-induced death or merely the concentration threshold.
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Selection of resistant mutants: Exposing bacteria to increasing concentrations of bacitracin or other cell wall antibiotics and characterizing the resulting resistant isolates for mutations in uppP and related genes.
These approaches collectively provide a comprehensive understanding of how uppP activity modulates antibiotic susceptibility across different classes of antibacterial agents .
