Recombinant Vibrio splendidus Protease HtpX (htpX)
Description
Molecular and Biochemical Characteristics
Key Features:
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Function: Categorized as a heat shock protein with potential proteolytic activity, though specific substrates remain uncharacterized.
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Structure: Contains domains characteristic of metalloproteases, including a conserved catalytic site requiring zinc ions .
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Thermal Stability: Optimal storage at -20°C/-80°C for liquid (6 months) and lyophilized forms (12 months) .
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Tagging: Tag type determined during manufacturing; no tag-specific data is publicly available.
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Quality Control: SDS-PAGE validation ensures >85% purity, with no reported contaminants .
Research Context and Gaps
While HtpX shares structural and functional similarities with other Vibrio metalloproteases (e.g., Vsm), no direct studies have been published on its enzymatic activity or role in pathogenicity. Current research focuses on:
Critical Gaps:
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Functional Annotation: HtpX’s catalytic targets and biological role remain undefined.
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Pathogenicity Link: No evidence ties HtpX directly to virulence in V. splendidus or other hosts.
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Regulation: Expression patterns and environmental triggers (e.g., temperature, stress) are unexplored.
Potential Applications
| Application | Rationale |
|---|---|
| Structural Biology | Study metalloprotease catalytic mechanisms and domain interactions. |
| Pathogen Research | Compare HtpX with Vsm to identify conserved virulence strategies. |
| Biotechnology | Explore biocatalytic potential in peptide processing or biofilm degradation. |
Product Specs
Note: While we prioritize shipping the format currently in stock, please specify your format preference during order placement for customized preparation.
Note: All proteins are shipped with standard blue ice packs. Dry ice shipping requires prior arrangement and incurs additional charges.
The tag type will be determined during production. To ensure a specific tag type, please inform us, and we will prioritize its development.
Target Background
KEGG: vsp:VS_2035
STRING: 575788.VS_2035
Q&A
What is Vibrio splendidus Protease HtpX and how does it function in bacterial cells?
HtpX is a membrane-bound zinc metalloprotease that participates in protein quality control within Vibrio splendidus. It belongs to the M50 family of metalloproteases and contains multiple transmembrane domains with a conserved HExxH motif in its catalytic domain. HtpX primarily functions to degrade misfolded or damaged membrane proteins, particularly under stress conditions, helping the bacterium maintain membrane homeostasis.
Methodological approach: To study HtpX function, researchers should employ gene deletion strategies similar to those described for other Vibrio proteases . Complementation assays using wild-type and catalytically inactive mutants can confirm phenotypes. Proteomics approaches comparing wild-type and htpX-deletion strains can identify accumulated substrate proteins and provide insights into the enzyme's physiological role.
How does HtpX differ from other metalloproteases in Vibrio species?
Unlike secreted metalloproteases such as Vsm that function primarily in virulence and environmental adaptation , HtpX is membrane-anchored and functions in intracellular protein quality control. While Vsm requires processing by other proteases for activation as shown in V. splendidus strain JZ6 , HtpX typically functions autonomously within the membrane. Additionally, their substrate specificities differ significantly: Vsm targets extracellular host proteins, whereas HtpX primarily targets misfolded membrane proteins within the bacterial cell.
Methodological approach: Comparative biochemical characterization of purified proteases using diverse synthetic substrates, combined with structural analysis, provides the clearest distinction between different Vibrio metalloproteases.
What are the optimal conditions for studying HtpX activity in vitro?
The optimal conditions for studying HtpX activity reflect both its biochemical requirements and the natural environment of Vibrio splendidus:
Methodological approach: Systematic optimization using factorial design experiments that test multiple parameters simultaneously helps identify true optima rather than local maxima.
What expression systems yield functional recombinant HtpX for biochemical studies?
The expression of membrane-bound metalloproteases like HtpX presents significant challenges requiring specialized approaches:
| Expression System | Advantages | Limitations | Yield |
|---|---|---|---|
| E. coli C41/C43 | Specialized for membrane proteins | Lower expression than standard strains | 0.5-2 mg/L |
| E. coli with pBAD vector | Tunable expression levels | Requires careful optimization | 1-3 mg/L |
| Cold-shock expression (16°C) | Improved folding | Extended cultivation time | 0.5-1.5 mg/L |
| Insect cells (baculovirus) | Better membrane protein folding | Higher cost, complex protocols | 2-5 mg/L |
| Cell-free systems | Avoids toxicity issues | Expensive, limited scale | 0.1-0.5 mg/reaction |
Methodological approach: Construct expression vectors with N-terminal fusion tags (His₁₀, MBP, or SUMO) to facilitate detection and purification. Optimize induction conditions (inducer concentration, temperature, duration) for each system to balance yield and proper folding.
What purification strategy yields the highest activity of recombinant HtpX?
A multi-step purification strategy optimized for membrane metalloproteases typically includes:
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Membrane fractionation through differential centrifugation
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Solubilization using mild detergents (preferably DDM or LMNG)
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Immobilized metal affinity chromatography (IMAC)
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Size exclusion chromatography to ensure homogeneity
Each step must be optimized to maintain enzyme activity:
| Purification Step | Critical Parameters | Activity Retention (%) |
|---|---|---|
| Membrane extraction | Gentle disruption methods | 80-90 |
| Detergent solubilization | LMNG at 1% (w/v) for 1h at 4°C | 70-80 |
| IMAC purification | Low imidazole in wash buffers (10-30 mM) | 60-70 |
| Size exclusion | Addition of 10% glycerol as stabilizer | 90-95 |
Methodological approach: Assess enzyme activity after each purification step to identify critical points of activity loss. Include zinc ions (0.1 mM ZnCl₂) in all buffers to maintain the metalloprotease active site integrity .
What are the most sensitive methods for measuring HtpX proteolytic activity?
Several complementary approaches provide comprehensive assessment of HtpX activity:
| Assay Method | Detection Limit | Advantages | Limitations |
|---|---|---|---|
| FRET peptide substrates | 0.1-1 nM enzyme | Real-time kinetics, high sensitivity | Requires knowledge of cleavage specificity |
| SDS-PAGE with model substrates | 5-10 nM enzyme | Visual confirmation of cleavage | Semi-quantitative, endpoint measurement |
| Mass spectrometry | 1-5 nM enzyme | Identifies exact cleavage sites | Requires specialized equipment |
| Circular dichroism | 50-100 nM enzyme | Monitors structural changes | Lower sensitivity |
| Isothermal titration calorimetry | 100-500 nM enzyme | Provides binding and catalytic parameters | Requires significant protein amounts |
Methodological approach: Begin with FRET-based assays using commercially available peptide libraries to identify potential substrates, followed by validation with more specific assays to determine precise cleavage mechanisms.
How does temperature affect HtpX activity and stability in Vibrio splendidus?
As V. splendidus is a marine bacterium adapted to moderate temperatures, HtpX activity shows temperature dependence reflecting its ecological niche:
Methodological approach: Measure initial reaction rates at various temperatures using standardized substrate concentrations, while conducting parallel stability studies to distinguish between temperature effects on catalytic rate versus enzyme denaturation.
How does HtpX contribute to Vibrio splendidus stress response mechanisms?
HtpX plays critical roles in bacterial stress response through several mechanisms:
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Degradation of misfolded membrane proteins that accumulate during stress conditions
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Maintenance of membrane integrity under temperature, osmotic, or oxidative stress
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Integration with other proteases in comprehensive protein quality control networks
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Processing of specific stress-related substrates that may influence signaling pathways
Methodological approach: Create htpX deletion mutants and assess their survival under various stress conditions (temperature shifts, oxidative agents, membrane-disrupting compounds). Complementation with wild-type htpX should restore stress tolerance, while catalytically inactive variants would not.
What is the relationship between HtpX activity and Vibrio splendidus virulence?
While specific information about HtpX's role in V. splendidus virulence remains limited, evidence from other Vibrio proteases suggests potential contributions:
| Potential Mechanism | Experimental Approach | Expected Results |
|---|---|---|
| Stress tolerance during host infection | Infection models with wild-type vs. ΔhtpX | Reduced colonization by mutant |
| Processing of virulence factors | Proteomics comparing secreted proteins | Altered processing patterns |
| Surface protein modification | Flow cytometry with surface markers | Changed surface antigen presentation |
| Biofilm formation | Crystal violet assays | Altered biofilm structure or stability |
Methodological approach: Compare wild-type and htpX mutant strains in virulence models, while identifying potential virulence-related substrates through comparative proteomics approaches .
How does quorum sensing affect HtpX expression and activity?
Quorum sensing (QS) likely regulates HtpX expression as part of the broader stress response network in Vibrio species:
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In V. harveyi, QS regulates expression of various proteases including metalloproteases
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QS systems respond to changes in cell density and environmental conditions
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The three-channel QS system described in Vibrio species integrates multiple signals that may influence htpX expression
Methodological approach: Quantitative RT-PCR (similar to methods described in ) comparing htpX expression in wild-type and QS mutant strains at different cell densities. Reporter gene fusions (htpX promoter driving luciferase) can provide real-time monitoring of expression in response to autoinducers.
How can CRISPR-Cas9 technology be applied to study HtpX function in Vibrio splendidus?
CRISPR-Cas9 offers several advantages for studying HtpX function:
| Application | Methodology | Expected Outcome |
|---|---|---|
| Gene deletion | Targeting htpX coding sequence | Complete loss-of-function phenotype |
| Point mutations | HDR-mediated modification of catalytic residues | Separation of catalytic vs. structural roles |
| Domain mapping | Precise truncations or internal deletions | Identification of functional domains |
| Protein tagging | C-terminal fluorescent protein fusion | Localization studies in live cells |
| CRISPRi | dCas9 targeting htpX promoter | Tunable repression for dosage studies |
Methodological approach: Design guide RNAs targeting conserved regions of htpX, optimize transformation protocols for V. splendidus, and develop appropriate selection strategies for identifying successful edits.
What proteomics approaches best identify the in vivo substrates of HtpX?
Several complementary proteomics approaches can identify physiological HtpX substrates:
| Approach | Principle | Advantages | Challenges |
|---|---|---|---|
| Comparative proteomics | Compare WT vs. ΔhtpX | Identifies accumulated substrates | Indirect identification |
| TAILS (Terminal Amine Isotopic Labeling) | Enriches for N-termini generated by proteolysis | Direct identification of cleavage sites | Technical complexity |
| Stable isotope labeling | Metabolic labeling combined with immunoprecipitation | Quantitative comparison | Requires efficient labeling |
| Proximity labeling | HtpX-BioID fusion labels nearby proteins | Identifies transient interactions | Potential false positives |
| Global protein stability profiling | Pulse-chase with stability measurements | Identifies proteins with altered half-lives | Labor intensive |
Methodological approach: Integrate multiple datasets for highest confidence in substrate identification, focusing on proteins that show evidence of HtpX-dependent processing across multiple techniques.
How can molecular dynamics simulations enhance understanding of HtpX catalytic mechanism?
Molecular dynamics simulations provide insights into aspects of HtpX function difficult to study experimentally:
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Modeling enzyme-substrate interactions in a membrane environment
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Investigating conformational changes during catalysis
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Simulating water accessibility to the active site within the membrane
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Predicting effects of mutations on structure and function
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Testing hypotheses about zinc coordination and the reaction mechanism
Methodological approach: Create a homology model based on related metalloproteases, embed it in a lipidic bilayer simulation system, and perform extended simulations (>100 ns) to observe relevant conformational dynamics. Validate computational predictions through site-directed mutagenesis and activity assays.
What controls are essential when studying recombinant HtpX activity?
Rigorous control experiments are critical for reliable HtpX research:
Methodological approach: Include all relevant controls in parallel with experimental samples, ensuring identical buffer conditions and incubation times to minimize variability.
How should conflicting or unexpected results in HtpX research be interpreted?
When faced with contradictory data, systematic troubleshooting approaches include:
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Verify enzyme integrity through activity assays and SDS-PAGE before each experiment
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Ensure metal cofactor availability by adding fresh ZnCl₂ to reaction buffers
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Check for interfering contaminants that may co-purify with the recombinant protein
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Test for detergent effects on activity and substrate accessibility
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Consider temperature-dependent effects on both enzyme activity and stability
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Evaluate buffer components for potential inhibitory effects
Methodological approach: Design experiments with internal controls that can identify sources of variability. When contradictory results persist, consider that they may reflect genuine biological complexity rather than technical artifacts.
