Recombinant Escherichia coli O8 UPF0059 membrane protein yebN (yebN)
Description
Membrane Topology and Domain Organization
The yebN protein is predicted to have multiple transmembrane segments that anchor it to the bacterial inner membrane. These transmembrane domains create a channel through which manganese ions and potentially other substrates can be transported. The protein's orientation within the membrane places specific domains in either the cytoplasmic or periplasmic spaces, allowing for interaction with various cellular components and regulatory proteins.
Functional Roles and Biological Significance
Studies on yebN homologs, particularly in Xanthomonas oryzae pv. oryzae (Xoo), have revealed that this protein functions primarily as a manganese (Mn²⁺) efflux system . This discovery is significant as it represents only the second known manganese export system identified in bacteria, highlighting the unique nature of this protein. Manganese ions play crucial roles in bacterial physiology, including protection against oxidative stress and contribution to virulence in pathogenic bacteria .
Experimental evidence from studies on the Xoo yebN homolog demonstrates that mutants lacking functional yebN accumulate abnormally high concentrations of intracellular manganese and exhibit increased sensitivity to elevated manganese levels in their environment . This observation confirms the protein's role in maintaining manganese homeostasis by facilitating the export of excess manganese ions from the bacterial cell.
Role in Oxidative Stress Response
This manganese-dependent response to oxidative stress suggests that yebN plays a critical role in detoxifying reactive oxygen species (ROS) through the regulation of intracellular manganese levels. The mechanism likely involves the balance between manganese's protective effects against oxidative damage and its potential toxicity at excessive concentrations.
Protection Against Hypo-osmotic Stress
Beyond its role in metal homeostasis and oxidative stress response, yebN appears to contribute to bacterial survival under hypo-osmotic conditions. Deletion of yebN in Xanthomonas rendered the bacteria significantly more sensitive to hypo-osmotic shock . This finding indicates that yebN may participate in maintaining cellular integrity during dramatic changes in environmental osmolarity, potentially through interactions with membrane components or other osmotic regulation systems.
Contribution to Bacterial Virulence
Perhaps most significantly from a medical and agricultural perspective, yebN has been implicated in bacterial virulence. Studies in Xanthomonas oryzae pv. oryzae demonstrated that mutation of yebN substantially reduced both bacterial growth rate and lesion formation in rice plants . This reduction in virulence suggests that yebN is essential for bacterial fitness within host environments and may represent a potential target for antimicrobial interventions.
The link between yebN function and virulence underscores the importance of metal homeostasis in host-pathogen interactions. By regulating manganese levels, yebN likely enables pathogenic bacteria to adapt to the metal-restricted environment within host tissues and to counter host defense mechanisms that rely on oxidative damage to eliminate invading microorganisms.
Regulation of yebN Expression
The expression of yebN appears to be tightly regulated in response to environmental conditions, particularly manganese concentrations. Research has shown that yebN expression is positively regulated by manganese and by the manganese-dependent transcription regulator MntR . This regulatory mechanism ensures that yebN production increases when manganese levels rise, enabling effective export of excess manganese and preventing cellular toxicity.
The precise molecular mechanisms of this regulation, including the identification of specific promoter elements and the details of MntR binding, represent important areas for future research. Understanding these regulatory pathways could provide insights into how bacteria modulate their response to changing metal concentrations and environmental conditions.
Production and Applications of Recombinant yebN
Recombinant production of yebN provides valuable research tools for studying the protein's structure, function, and potential applications. Available recombinant yebN proteins typically consist of the full-length 188 amino acid sequence, sometimes with additional tag sequences to facilitate purification and detection . These recombinant proteins are commonly expressed in bacterial systems and purified using standard chromatographic techniques.
Comparison with Related Proteins
YebN belongs to the UPF0059 family of membrane proteins, which includes homologs across various bacterial species. While the core functions appear to be conserved, species-specific variations may exist in terms of substrate specificity, regulatory mechanisms, and contributions to virulence. Table 1 presents a comparison of key features between yebN in different bacterial species.
| Table 1: Comparison of YebN Features Across Bacterial Species |
|---|
| Feature |
| Primary Function |
| Domain Structure |
| Role in Virulence |
| Stress Response |
| Regulation |
Another interesting protein that shares some structural features with yebN is YejM, an essential inner membrane protein in E. coli and Salmonella typhimurium. Unlike yebN, YejM functions as a metalloenzyme with phosphatase activity dependent on magnesium ions and plays a critical role in outer membrane remodeling . Despite their distinct functions, both proteins highlight the diverse roles of membrane-associated metalloenzymes in bacterial physiology.
YebN in E. coli O-Antigen Context
The O-antigen is a critical component of the lipopolysaccharide (LPS) in the outer membrane of gram-negative bacteria like E. coli. Different O-antigen structures define the various E. coli serogroups, which can be associated with different virulence properties and host interactions . The E. coli O-antigen varies considerably, with 176 different structures identified among the 181 E. coli O-antigens .
Most (93%) of these O-antigens are synthesized via the Wzx/Wzy pathway, while 11 utilize the ABC transporter pathway . While specific information about yebN's role in the context of E. coli O-antigen synthesis is limited, understanding the relationship between membrane proteins like yebN and O-antigen structure could provide insights into bacterial membrane organization and host-pathogen interactions.
Future Research Directions
Despite significant advances in understanding yebN function, several important questions remain unanswered, particularly regarding the protein's role in E. coli. Future research directions might include:
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Detailed structural analysis of E. coli yebN using advanced techniques such as cryo-electron microscopy or X-ray crystallography
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Investigation of yebN's specific role in E. coli virulence and stress response
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Exploration of potential interactions between yebN and other membrane components, including those involved in O-antigen synthesis
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Development of inhibitors targeting yebN as potential antimicrobial agents
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Comparative studies of yebN across different E. coli serotypes to identify strain-specific variations
Product Specs
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The tag type is determined during production. If you require a specific tag, please inform us, and we will prioritize its development.
Target Background
KEGG: ecr:ECIAI1_1891
Q&A
What is the basic structure and characteristics of Recombinant E. coli O8 UPF0059 membrane protein yebN?
Recombinant E. coli O8 UPF0059 membrane protein yebN is a full-length protein (1-188 amino acids) derived from Escherichia coli O8 strain IAI1. When produced recombinantly, it is typically expressed with an N-terminal His-tag to facilitate purification and detection. The protein is supplied as a lyophilized powder and is expressed in E. coli expression systems .
As a membrane protein, yebN is integrated into the bacterial cell membrane, though its specific topology and structural characteristics require further characterization through techniques such as crystallography or cryo-electron microscopy.
How does yebN protein fit into the classification of E. coli membrane proteins?
E. coli membrane proteins fall into two primary architectural categories: helix bundle proteins and β-barrel proteins. While helix bundle proteins have been extensively studied and can be reliably predicted from sequence data alone, β-barrel proteins have received comparatively less attention in bioinformatics .
Based on current classification systems, membrane proteins like yebN can be identified through bioinformatics prediction tools such as the Hunter predictor, which has been successfully used to identify other membrane proteins in E. coli. These tools analyze sequence characteristics to predict membrane localization and topology, though experimental verification is essential for confirming these predictions .
What expression systems are most effective for producing functional recombinant yebN protein?
The E. coli expression system is the preferred method for producing recombinant yebN protein, as demonstrated by successful production of His-tagged full-length protein (1-188aa) . For optimal expression of membrane proteins like yebN, consider the following methodological approach:
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Vector selection: Use vectors with tunable promoters (like arabinose-inducible systems) that allow controlled expression
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Host strain optimization: BL21(DE3) derivatives or C41/C43 strains specially designed for membrane protein expression
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Growth conditions: Lower temperatures (16-25°C) during induction to slow protein synthesis and facilitate proper folding
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Inducer concentration: Titrate inducer levels to prevent formation of inclusion bodies
This approach is based on protocols that have succeeded with other E. coli membrane proteins, where carefully controlled expression conditions significantly improve the yield of correctly folded protein .
What purification strategies maximize yield and maintain the structural integrity of yebN?
Purification of membrane proteins like yebN requires specialized approaches to maintain their native conformation. A recommended multistep purification protocol includes:
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Membrane fraction isolation: Separate outer and inner membranes using sucrose gradient centrifugation (two- and six-step gradients)
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Detergent solubilization: Screen multiple detergents (DDM, LDAO, OG) for optimal solubilization
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Affinity chromatography: Utilize the His-tag for IMAC purification under optimized detergent conditions
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Quality control: Verify membrane integration versus aggregation through urea washing (5M urea) of purified fractions
This approach distinguishes between true membrane-integrated proteins and aggregated proteins that may co-sediment with membrane fractions . Verification of proper membrane integration can be performed using techniques similar to those that confirmed other E. coli outer membrane proteins.
How can we experimentally verify the membrane localization of yebN protein?
Experimental verification of membrane localization for proteins like yebN involves a systematic approach similar to methods used for other E. coli membrane proteins:
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Cell fractionation: Separate cellular compartments through differential centrifugation
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Membrane separation: Isolate inner and outer membranes using sucrose density gradient centrifugation
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Validation of fraction purity: Perform Western blotting against known inner membrane (e.g., Lep) and outer membrane (e.g., OmpA) marker proteins
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Urea washing test: Treat membrane fractions with 5M urea to distinguish between true membrane-integrated proteins and aggregates
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Detection: Use antibodies against the His-tag to identify the target protein in membrane fractions
This methodology has successfully confirmed the membrane localization of proteins like YftM, YaiO, YfaZ, CsgF, and YliI, and can be applied to verify yebN localization .
What techniques are most effective for studying the topology and orientation of yebN in the membrane?
Understanding the topology and orientation of membrane proteins like yebN requires multiple complementary approaches:
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Protease accessibility assays: Treat intact cells or spheroplasts with proteases to determine exposed regions
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Cysteine scanning mutagenesis: Introduce cysteine residues at various positions followed by labeling with membrane-impermeable reagents
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GFP-fusion analysis: Create fusions with GFP at different termini and internal sites to determine cellular localization
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FRET analysis: Measure distances between labeled regions to map structural organization
These techniques provide complementary data that, when integrated, can create a comprehensive model of how yebN is oriented within the membrane, which is essential for understanding its function.
What are the primary research applications for recombinant yebN protein?
Recombinant proteins like yebN serve multiple purposes in both basic and translational research:
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Functional studies: Elucidating the biological role of yebN in E. coli membrane biology
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Structural biology: Determining three-dimensional structure through X-ray crystallography or cryo-EM
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Protein-protein interaction studies: Identifying binding partners through pull-down assays or cross-linking experiments
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Antibody production: Generating specific antibodies for detection and localization studies
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Drug discovery: Potential target for antimicrobial development if functions prove essential
As with other recombinant proteins, yebN allows researchers to perform in vitro and in vivo studies to decipher the function of the endogenously expressed protein, contributing to our understanding of basic biological pathways at both cellular and organismal levels .
How does the study of yebN contribute to our understanding of bacterial membrane biology?
The study of membrane proteins like yebN contributes significantly to our understanding of bacterial membrane biology in several ways:
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Membrane proteome completion: Identifying and characterizing previously unannotated membrane proteins helps complete the E. coli membrane proteome
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Membrane biogenesis: Understanding how proteins are targeted to and inserted into specific membrane compartments
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Bacterial physiology: Determining functions that may be critical for bacterial survival or adaptation
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Comparative biology: Comparing membrane protein families across bacterial species for evolutionary insights
Bioinformatics prediction followed by experimental verification of membrane proteins like yebN represents an important complementary approach to large-scale proteomics for identifying bacterial membrane proteins, particularly those that are expressed at low levels or only under specific conditions .
How can researchers troubleshoot issues with yebN expression and membrane integration?
When facing challenges with expression and membrane integration of yebN, consider this systematic troubleshooting approach:
| Issue | Potential Causes | Solutions |
|---|---|---|
| Low expression yield | Toxicity, codon bias, promoter strength | Test different promoters, use Rosetta strains for rare codons, optimize induction conditions |
| Protein degradation | Protease activity, instability | Add protease inhibitors, reduce temperature, use protease-deficient strains |
| Inclusion body formation | Overexpression, improper folding | Reduce inducer concentration, lower temperature, add folding enhancers |
| Poor membrane integration | Inefficient translocation, signal sequence issues | Verify SecA-dependent translocation, analyze signal sequence, test SecB dependence |
| Aggregation during purification | Detergent incompatibility, concentration issues | Screen detergent panel, optimize protein:detergent ratio |
As observed with other E. coli membrane proteins, SecB chaperone dependence may be crucial for proper targeting of yebN to the membrane. This can be tested by analyzing protein localization in SecB-deficient strains or by performing pulse-chase experiments in the presence of azide to block SecA-dependent translocation .
What advanced analytical techniques can reveal structural and functional aspects of yebN?
Advanced analytical techniques provide deeper insights into yebN structure and function:
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Hydrogen-deuterium exchange mass spectrometry (HDX-MS): Map solvent-accessible regions and conformational dynamics
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Single-particle cryo-EM: Determine high-resolution structure in a near-native environment
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Solid-state NMR: Analyze protein structure and dynamics within the membrane
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Native mass spectrometry: Characterize protein-lipid interactions and oligomeric states
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Molecular dynamics simulations: Model protein behavior within the membrane environment
These techniques go beyond basic characterization to provide mechanistic insights into how yebN functions within the membrane context, potentially revealing functional motifs, conformational changes, or interaction interfaces critical to its biological role.
What functional assays can be used to determine the biological activity of yebN?
While the precise function of yebN has yet to be fully characterized, several methodological approaches can be employed to investigate its potential activities:
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Transport assays: If yebN functions as a transporter, radioactive or fluorescently labeled substrates can be used to measure transport activity across membrane vesicles or reconstituted proteoliposomes
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Electrophysiology: Patch-clamp or planar lipid bilayer recordings to detect potential channel or pore-forming activities
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Growth complementation: Test whether yebN expression can rescue growth defects in mutant strains lacking specific membrane functions
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Protein-protein interaction assays: BioID or APEX2 proximity labeling to identify proteins that interact with yebN in its native environment
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Phenotypic screens: Characterize phenotypes resulting from yebN deletion or overexpression under various stress conditions
These functional assays should be designed based on bioinformatic predictions of potential functions and complemented with appropriate controls to ensure specificity.
How can researchers distinguish between direct and indirect effects when studying yebN function?
Distinguishing direct from indirect effects requires rigorous experimental design:
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Site-directed mutagenesis: Create point mutations in conserved residues to identify those critical for function
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Inducible expression systems: Use tightly controlled expression to examine immediate vs. long-term effects
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In vitro reconstitution: Purify yebN and reconstitute in defined liposome systems to test direct functions
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Time-course experiments: Monitor cellular responses immediately following yebN induction
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Comparative analysis: Test multiple homologs from different bacterial species to identify conserved functions
This multilayered approach helps establish causality and differentiate direct functional roles from secondary cellular adaptations, providing stronger evidence for the true biological function of yebN.
How conserved is yebN across bacterial species and what does this suggest about its function?
Understanding the evolutionary conservation of yebN provides important functional insights:
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Conduct comparative genomic analysis across diverse bacterial species to identify homologs
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Align sequences to identify highly conserved residues that may be functionally critical
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Construct phylogenetic trees to map evolutionary relationships
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Analyze gene neighborhood conservation (synteny) which often indicates functional relationships
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Compare expression patterns across species under various conditions
Proteins with essential functions tend to be highly conserved, while those involved in specific adaptations may show greater variability or restricted distribution. The approach used to identify other E. coli membrane proteins through bioinformatics prediction and experimental verification can be extended to study yebN conservation across species .
What genetic approaches can reveal the physiological role of yebN in E. coli?
Genetic approaches provide powerful tools for understanding yebN function:
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Gene knockout studies: Create clean deletion mutants and characterize phenotypes under various conditions
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Complementation analysis: Test whether wild-type yebN can rescue knockout phenotypes
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Suppressor screens: Identify mutations that suppress phenotypes of yebN deletion or overexpression
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Synthetic lethality screens: Find genes that become essential when yebN is deleted
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Transcriptional profiling: Compare global gene expression changes in response to yebN deletion or overexpression
This genetic toolkit reveals the cellular pathways affected by yebN, helping to place it within the broader context of E. coli physiology and potentially identifying conditions where its function becomes critical.
How might structural determination of yebN advance our understanding of UPF0059 family proteins?
Structural determination of yebN would significantly advance membrane protein research:
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Identify structural motifs that define the UPF0059 family
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Reveal potential substrate binding sites or channel-forming regions
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Provide templates for modeling homologous proteins across species
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Enable structure-based functional predictions and hypotheses
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Guide the design of specific inhibitors or activators for functional studies
The techniques used to study membrane proteins like yebN are similar to those that have successfully characterized other E. coli membrane proteins, where bioinformatics predictions guided experimental approaches to confirm structural features .
What are the potential implications of yebN research for antimicrobial development?
If yebN proves to have an essential function in E. coli, it could represent a novel target for antimicrobial development:
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Target validation: Determine if yebN is essential for bacterial survival or virulence
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High-throughput screening: Develop assays to identify compounds that modulate yebN function
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Structure-based drug design: Use structural information to design specific inhibitors
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Species selectivity analysis: Compare yebN across pathogens and commensal bacteria to ensure target specificity
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Resistance mechanism exploration: Investigate potential mechanisms by which bacteria might develop resistance to yebN-targeted therapies
This research pathway follows established approaches for developing antimicrobials against membrane protein targets, where understanding protein structure and function guides therapeutic development strategies.
