Recombinant Probable intracellular septation protein A (VP1970)

What is Probable intracellular septation protein A (VP1970) and what organism does it originate from?

Probable intracellular septation protein A (VP1970) is a membrane-spanning protein found in Vibrio parahaemolyticus Serotype O3:K6. It is classified as an inner membrane-spanning protein with the gene name VP1970 and is also known as YciB in some contexts. The protein consists of 187 amino acids and has a UniProt ID of Q87NA5 . Based on its designation as a septation protein, it likely plays a role in bacterial cell division processes, particularly in the formation of the septum during binary fission. The protein's localization in the inner membrane suggests it may be involved in membrane organization or remodeling during cell division, though its precise function requires further characterization through targeted research approaches.

How stable is recombinant VP1970 protein under different storage conditions?

Recombinant VP1970 protein exhibits variable stability depending on storage conditions. For optimal stability, the lyophilized powder form should be stored at -20°C to -80°C upon receipt. After reconstitution, working aliquots can be maintained at 4°C for up to one week, but repeated freeze-thaw cycles should be avoided as they can significantly reduce protein integrity and activity .

The protein is typically stored in Tris/PBS-based buffer with 6% trehalose at pH 8.0, which helps maintain stability during freeze-thaw cycles. For long-term storage, it is recommended to add glycerol to a final concentration of 5-50% (with 50% being optimal) and store in aliquots at -20°C to -80°C . Under these conditions, the protein can maintain structural integrity for several months, though activity testing is recommended before critical experiments if the protein has been stored for extended periods.

What expression systems are most effective for producing recombinant VP1970?

E. coli expression systems have proven to be the most effective for producing recombinant VP1970 protein . When designing expression constructs, several factors should be considered:

• Codon optimization: Adapting the VP1970 gene sequence to E. coli codon usage preferences improves translation efficiency and protein yield.

• Fusion tags: N-terminal His-tags are commonly employed to facilitate purification while maintaining protein functionality. The His-tag allows for efficient one-step purification using immobilized metal affinity chromatography (IMAC) .

• Expression vectors: pET-series vectors under the control of T7 promoter systems offer high expression levels and inducible control with IPTG.

• Host strains: BL21(DE3) derivatives are preferred due to their reduced protease activity and compatibility with T7 expression systems.

For membrane proteins like VP1970, specialized E. coli strains such as C41(DE3) or C43(DE3) may provide improved expression by accommodating the potential toxicity associated with membrane protein overexpression. Temperature modulation (typically lowering to 16-25°C after induction) and reduced IPTG concentrations (0.1-0.5 mM) often enhance soluble protein yields compared to standard conditions.

What purification strategy yields the highest purity of recombinant VP1970?

A multi-step purification strategy yields the highest purity (>90%) of recombinant His-tagged VP1970 protein. The recommended protocol involves:

• Initial extraction: Use appropriate detergents (e.g., n-dodecyl β-D-maltoside or CHAPS) to solubilize the membrane-bound protein.

• IMAC purification: Apply the solubilized protein to Ni-NTA or cobalt-based affinity resins, exploiting the N-terminal His-tag for selective binding .

• Washing steps: Use increasing imidazole concentrations (10-40 mM) in washing buffers to remove non-specifically bound proteins.

• Elution: Employ high imidazole concentration (250-500 mM) to elute the target protein.

• Secondary purification: Subject the eluted protein to size exclusion chromatography to remove aggregates and further enhance purity.

• Quality control: Confirm purity through SDS-PAGE analysis, which should exceed 90% for most research applications .

• Endotoxin removal: For cell-based assays, additional endotoxin removal steps may be necessary.

For applications requiring ultra-high purity, ion exchange chromatography can be integrated between the IMAC and size exclusion steps. The final purified protein should be rapidly concentrated, buffer-exchanged into a stabilizing formulation, and lyophilized or stored with glycerol to prevent degradation.

How can researchers optimize the reconstitution process for lyophilized VP1970?

Optimizing the reconstitution process for lyophilized VP1970 requires careful attention to several parameters:

• Initial preparation: Centrifuge the vial briefly (30 seconds at 10,000×g) before opening to ensure all material is at the bottom .

• Reconstitution medium: Use deionized sterile water with a target protein concentration of 0.1-1.0 mg/mL. The specific buffer composition can significantly impact protein stability and activity .

• Reconstitution method: Add reconstitution medium slowly while gently rotating the vial to ensure complete dissolution without generating foam. Avoid vigorous shaking or vortexing, which can cause protein denaturation.

• Stabilizing additives: Add glycerol to a final concentration of 5-50% after reconstitution. The recommended concentration is 50% for maximum stability during storage .

• Equilibration time: Allow the reconstituted protein to stand at room temperature for 10-15 minutes, followed by gentle mixing to ensure complete solubilization.

• Aliquoting strategy: Divide the reconstituted protein into single-use aliquots based on experimental requirements to avoid repeated freeze-thaw cycles.

• Quality verification: Before experimental use, verify protein integrity via Western blot or functional assays to ensure the reconstitution process preserved protein structure and activity.

For membrane proteins like VP1970, including low concentrations of detergents (0.01-0.05% n-dodecyl β-D-maltoside) in the reconstitution buffer can help maintain solubility and prevent aggregation during the reconstitution process.

How can VP1970 be utilized in protein-protein interaction studies?

VP1970 can be effectively utilized in protein-protein interaction studies through several complementary approaches:

• Co-immunoprecipitation (Co-IP): Similar to the techniques demonstrated with other proteins in the literature, researchers can use antibodies against VP1970 (or its tag) to pull down potential interacting partners from cell lysates . The experimental design should include:

  • Appropriate negative controls (non-specific IgG, lysates from cells not expressing VP1970)

  • Crosslinking optimization if interactions are transient

  • Detergent selection appropriate for membrane protein interactions

• Bimolecular Fluorescence Complementation (BiFC): By creating fusion proteins with split fluorescent protein fragments (e.g., split-YFP), researchers can visualize VP1970 interactions within living bacterial cells.

• Bacterial Two-Hybrid (B2H) System: Particularly useful for bacterial proteins, B2H systems can detect interactions through transcriptional activation of reporter genes when two proteins of interest interact.

• Pull-down assays: Use purified His-tagged VP1970 as bait protein immobilized on Ni-NTA resin to capture interacting partners from cellular lysates.

• Surface Plasmon Resonance (SPR): For quantitative binding kinetics, immobilize purified VP1970 on a sensor chip and measure real-time binding of potential interacting proteins.

These approaches can elucidate VP1970's potential role in septation by identifying interactions with other division proteins, membrane components, or cytoskeletal elements involved in bacterial cell division.

What methodologies are recommended for studying VP1970 localization in bacterial cells?

To study VP1970 localization in bacterial cells, researchers should employ multiple complementary methodologies:

• Fluorescent Protein Fusions: Create C- or N-terminal fusions of VP1970 with fluorescent proteins (e.g., GFP, mCherry). When designing these constructs:

  • Validate that the fusion doesn't disrupt protein function through complementation assays

  • Use linker sequences to minimize structural interference

  • Express from native promoters when possible to maintain physiological expression levels

• Immunofluorescence Microscopy: Use specific antibodies against VP1970 or its tag, coupled with:

  • Optimized fixation protocols for membrane proteins (e.g., gentle fixation with 2% paraformaldehyde)

  • Membrane permeabilization conditions suitable for accessing inner membrane epitopes

  • Co-staining with markers for cell division sites (e.g., FtsZ) and membrane domains

• Super-resolution Microscopy: Techniques such as STORM, PALM, or structured illumination microscopy provide nanoscale resolution of VP1970 localization patterns relative to other cellular structures.

• Time-lapse Imaging: To correlate VP1970 dynamics with cell cycle progression, incorporating:

  • Microfluidic devices for long-term observation

  • Dual-color imaging with cell division markers

  • Quantitative analysis of protein redistribution during division events

• Fractionation Studies: Biochemical fractionation of bacterial membranes can confirm VP1970's subcellular localization and potential association with specific membrane microdomains.

These approaches will help determine whether VP1970 localizes to the septum during division, associates with specific membrane regions, or shows dynamic redistribution during the bacterial cell cycle.

How can researchers investigate the functional role of VP1970 in bacterial septation?

Investigating the functional role of VP1970 in bacterial septation requires a multi-faceted approach:

• Gene Deletion and Complementation: Generate a VP1970 knockout strain in Vibrio parahaemolyticus and assess:

  • Cell morphology changes using phase contrast and electron microscopy

  • Growth kinetics under various conditions

  • Division site placement and frequency of septation events

  • Complementation with wild-type VP1970 to confirm phenotype specificity

• Site-Directed Mutagenesis: Create point mutations in conserved residues or domains to:

  • Identify critical functional regions

  • Distinguish between structural and catalytic roles

  • Assess the importance of specific transmembrane segments

• Protein Depletion Systems: Use conditional expression systems to deplete VP1970 and observe acute effects on:

  • Septum formation using membrane-specific dyes

  • Recruitment of other division proteins to the division site

  • Cell wall synthesis patterns at division sites

• Protein-Protein Interaction Network Mapping: Identify VP1970's interaction partners within the divisome complex using:

  • Systematic bacterial two-hybrid screening

  • Co-immunoprecipitation with mass spectrometry

  • Proximity-based labeling approaches (e.g., BioID)

• In vitro Reconstitution: Purify VP1970 and assess its ability to:

  • Alter membrane properties in synthetic vesicles

  • Interact with lipid bilayers of varying compositions

  • Influence the assembly of other division proteins on membranes

These approaches will collectively provide insights into whether VP1970 plays a structural role in septum formation, regulates the recruitment or activity of other division proteins, or directly participates in membrane remodeling during cell division.

What strategies exist for intracellular delivery of VP1970 in eukaryotic systems?

Intracellular delivery of VP1970 in eukaryotic systems presents unique challenges due to the membrane-impermeability of proteins. Several advanced strategies can be employed:

• Direct Protein Engineering Approaches:

  • Fusion with cell-penetrating peptides (CPPs) such as TAT, penetratin, or polyarginine sequences

  • Engineering with endosomal escape domains to improve cytosolic access following endocytosis

  • Incorporation of pH-responsive elements that facilitate membrane disruption under endosomal conditions

• Nanocarrier-Mediated Delivery Systems:

  • Lipid nanoparticles formulated with fusogenic lipids

  • Polymer-based carriers with endosomolytic properties

  • Protein-based carriers such as engineered exosomes or virus-like particles

• Physical Methods:

  • Electroporation for transient membrane permeabilization

  • Microinjection for direct cytoplasmic delivery in specific cells

  • Sonoporation using ultrasound in combination with microbubbles

• Cell-Penetrating Antibody Technology:

  • Adaptation of cytotransmab technology, which uses cationic residues to interact with heparan sulfate proteoglycans followed by endosomal escape mechanisms

  • Engineering pH-dependent conformational changes to facilitate endosomal escape

• Photochemical Internalization:

  • Combining VP1970 with photosensitizers that disrupt endosomal membranes upon light activation

When selecting a delivery method, researchers must consider the specific experimental requirements, target cell types, and potential interference with VP1970's native function. Validation of successful cytosolic delivery should include confocal microscopy with appropriate markers to distinguish between endosomal entrapment and true cytosolic localization.

How can structural analysis techniques be applied to characterize VP1970?

Comprehensive structural characterization of VP1970 requires a multi-technique approach suitable for membrane proteins:

• X-ray Crystallography:

  • Detergent screening to identify optimal solubilization conditions

  • Lipidic cubic phase crystallization methods for membrane proteins

  • Use of crystallization chaperones such as antibody fragments to provide crystal contacts

• Cryo-Electron Microscopy (cryo-EM):

  • Single-particle analysis for high-resolution structure determination

  • Integration with nanodiscs or amphipols to maintain native-like membrane environment

  • Classification algorithms to address conformational heterogeneity

• Nuclear Magnetic Resonance (NMR) Spectroscopy:

  • Solution NMR for dynamic regions and flexible domains

  • Solid-state NMR for transmembrane regions in lipid environments

  • Selective isotopic labeling strategies to simplify spectra

• Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS):

  • Analysis of solvent-accessible regions and conformational dynamics

  • Mapping protein-protein interaction surfaces

  • Detergent-compatible workflows for membrane proteins

• Molecular Dynamics Simulations:

  • Integration of experimental data with computational models

  • Simulation of VP1970 in explicit lipid bilayers

  • Analysis of conformational states and transitions

• Circular Dichroism (CD) Spectroscopy:

  • Secondary structure content estimation

  • Thermal stability assessment

  • Detergent and lipid composition effects on structure

The combination of these techniques would provide complementary information about VP1970's topology, secondary and tertiary structure, dynamics, and interactions with the membrane environment. This structural information is crucial for understanding the protein's mechanistic role in bacterial septation and for designing rational mutagenesis experiments.

What approaches can be used to investigate post-translational modifications of VP1970?

Investigation of post-translational modifications (PTMs) of VP1970 requires specialized analytical approaches:

• Mass Spectrometry-Based Proteomics:

  • High-resolution LC-MS/MS analysis of purified VP1970

  • Enrichment strategies for specific modifications (phosphopeptides, glycopeptides)

  • Various fragmentation methods (HCD, ETD, EThcD) to improve PTM localization

  • Quantitative approaches (SILAC, TMT) to compare modification levels under different conditions

• Site-Specific Antibodies:

  • Generation of antibodies against predicted modification sites

  • Western blotting to detect presence/absence of modifications

  • Immunoprecipitation to enrich modified forms for further analysis

• Genetic Approaches:

  • Mutagenesis of potential modification sites (Ser/Thr/Tyr for phosphorylation, Lys for acetylation/ubiquitination)

  • Expression in systems lacking specific modifying enzymes

  • Phenotypic analysis of modification-site mutants

• Metabolic Labeling:

  • Incorporation of radioactive precursors (^32P-orthophosphate for phosphorylation)

  • Click chemistry-compatible analogs for tracking lipid modifications

  • Pulse-chase experiments to determine modification dynamics

• In vitro Modification Assays:

  • Incubation of purified VP1970 with candidate modifying enzymes

  • Analysis of modification status before and after treatment

  • Functional consequences of modifications on protein activity

For membrane proteins like VP1970, special consideration must be given to sample preparation to ensure complete extraction and maintain modification integrity. The analysis should focus particularly on modifications that might regulate membrane association, protein-protein interactions, or conformational changes relevant to septation processes.

What are common challenges in achieving high expression yields of VP1970, and how can they be addressed?

Membrane proteins like VP1970 present several challenges for high-yield expression:

• Toxicity to Expression Host:

  • Challenge: Overexpression can disrupt host membrane integrity

  • Solution: Use C41(DE3) or C43(DE3) E. coli strains specifically developed for toxic membrane proteins

  • Solution: Implement tightly controlled inducible expression systems with tunable promoters

• Inclusion Body Formation:

  • Challenge: Protein misfolding and aggregation

  • Solution: Lower induction temperature (16-20°C)

  • Solution: Reduce inducer concentration (0.1-0.2 mM IPTG)

  • Solution: Co-express chaperones (GroEL/GroES, DnaK/DnaJ)

• Limited Membrane Capacity:

  • Challenge: Saturation of membrane insertion machinery

  • Solution: Use strains with expanded membrane surface area

  • Solution: Extend expression time while maintaining lower inducer levels

  • Solution: Sequential induction protocols with recovery periods

• Protein Degradation:

  • Challenge: Host proteases targeting misfolded protein

  • Solution: Use protease-deficient strains (e.g., BL21)

  • Solution: Include protease inhibitors during extraction

  • Solution: Optimize extraction timing to harvest before degradation occurs

• Purification Efficiency:

  • Challenge: Incomplete solubilization from membranes

  • Solution: Screen multiple detergents (DDM, LDAO, CHAPS)

  • Solution: Optimize detergent:protein ratios

  • Solution: Consider nanodiscs or amphipols for maintaining native environment

Implementing a systematic optimization approach addressing these factors can significantly improve yields. Experimental design should include small-scale expression tests varying multiple parameters (strain, temperature, inducer concentration, duration) before scaling up to production quantities.

How can researchers troubleshoot problems with VP1970 solubility and stability?

Troubleshooting VP1970 solubility and stability issues requires a systematic approach:

• Detergent Optimization:

  • Problem: Insufficient solubilization or protein aggregation

  • Solution: Screen detergent panel (mild: DDM, LMNG; moderate: DM; harsh: SDS)

  • Solution: Test detergent concentrations (1-5× critical micelle concentration)

  • Solution: Evaluate detergent mixtures for synergistic effects

• Buffer Composition:

  • Problem: pH-dependent aggregation or unfolding

  • Solution: Screen pH range (6.0-9.0) for optimal stability

  • Solution: Test various buffer systems (Tris, HEPES, phosphate)

  • Solution: Evaluate ionic strength effects (100-500 mM NaCl)

• Stabilizing Additives:

  • Problem: Time-dependent loss of activity or structural integrity

  • Solution: Add glycerol (5-20%) to reduce hydrophobic aggregation

  • Solution: Include specific lipids that may be required for stability

  • Solution: Test osmolytes (trehalose, sucrose) as stabilizing agents

• Temperature Sensitivity:

  • Problem: Thermal instability during handling

  • Solution: Maintain samples at 4°C during all purification steps

  • Solution: Add stabilizers specific for thermal protection

  • Solution: Determine thermal denaturation profile using differential scanning fluorimetry

• Oxidation Sensitivity:

  • Problem: Cysteine-mediated aggregation or inactivation

  • Solution: Include reducing agents (DTT, TCEP)

  • Solution: Work under nitrogen atmosphere for sensitive proteins

  • Solution: Consider site-directed mutagenesis of non-essential cysteines

A systematic stability screen recording protein behavior under various conditions (using techniques like size-exclusion chromatography, dynamic light scattering, and activity assays) can create a stability phase diagram to identify optimal conditions for handling VP1970 throughout experimental workflows.

What analytical techniques can verify the correct folding and functionality of recombinant VP1970?

Verifying correct folding and functionality of recombinant VP1970 requires multiple complementary analytical techniques:

• Circular Dichroism (CD) Spectroscopy:

  • Far-UV CD (190-260 nm) to assess secondary structure content

  • Thermal melting curves to determine protein stability

  • Comparison with predicted secondary structure from sequence analysis

• Intrinsic Fluorescence Spectroscopy:

  • Tryptophan fluorescence emission spectra to probe tertiary structure

  • Red-shift analysis to evaluate solvent exposure of aromatic residues

  • Quenching studies to assess accessibility of fluorophores

• Size Exclusion Chromatography with Multi-Angle Light Scattering (SEC-MALS):

  • Determination of oligomeric state and homogeneity

  • Detection of aggregation or degradation products

  • Analysis of detergent/lipid content in protein-detergent complexes

• Functional Binding Assays:

  • Pull-down assays with known interaction partners

  • Surface plasmon resonance for quantitative binding parameters

  • Fluorescence anisotropy for measuring interactions in solution

• Membrane Association Studies:

  • Liposome binding assays to verify membrane interaction capability

  • Proteoliposome reconstitution to assess membrane integration

  • Electron microscopy to visualize membrane morphology changes

• Cellular Complementation Assays:

  • Expression in VP1970-deficient strains to verify functional complementation

  • Microscopy-based assessment of cell morphology and division

  • Growth phenotype rescue under various stress conditions

The integration of these biophysical and functional approaches provides a comprehensive assessment of protein quality. For membrane proteins like VP1970, special emphasis should be placed on techniques compatible with detergent-solubilized samples or reconstituted membrane systems to ensure relevance to the protein's native environment.

How might VP1970 research contribute to understanding bacterial cell division mechanisms?

Research on VP1970 has significant potential to advance our understanding of bacterial cell division mechanisms in several key areas:

• Membrane Dynamics During Division:

  • Investigation of VP1970's role in membrane curvature generation or stabilization

  • Analysis of lipid domain organization at division sites

  • Elucidation of protein-lipid interactions essential for septum formation

• Division Machinery Coordination:

  • Mapping VP1970's position within the hierarchical assembly of divisome components

  • Determining temporal recruitment patterns relative to other division proteins

  • Identifying regulatory interactions that coordinate membrane and peptidoglycan remodeling

• Species-Specific Division Mechanisms:

  • Comparative analysis of VP1970 homologs across bacterial species

  • Identification of conserved and divergent functional domains

  • Correlation of structural differences with variations in division processes

• Environmental Adaptation:

  • Examination of VP1970's role in division under various stress conditions

  • Analysis of expression regulation in response to environmental signals

  • Potential involvement in stress-induced morphological transitions

• Evolutionary Perspectives:

  • Phylogenetic analysis of YciB/VP1970 protein family evolution

  • Identification of ancestral functions and specialized adaptations

  • Correlation with bacterial morphological diversity

These investigations would complement existing knowledge of core division machinery (FtsZ, FtsA, etc.) by specifically addressing the membrane remodeling aspects of division. Given that VP1970 is classified as a "probable" septation protein, definitive functional characterization would fill an important gap in our understanding of the complete divisome assembly and function.

What potential applications exist for VP1970 in antimicrobial development?

VP1970 presents several promising avenues for antimicrobial development:

• Target-Based Drug Discovery:

  • If essential for Vibrio parahaemolyticus viability, VP1970 could serve as a direct drug target

  • Structure-based design of small molecules targeting critical VP1970 functional domains

  • Fragment-based screening against purified VP1970 to identify initial chemical matter

• Peptide Inhibitor Development:

  • Design of peptides mimicking interaction interfaces between VP1970 and division partners

  • Development of stapled peptides for enhanced stability and membrane permeability

  • Phage display screening to identify high-affinity binding peptides

• Combination Therapy Approaches:

  • Targeting VP1970 to sensitize bacteria to existing cell wall-targeting antibiotics

  • Dual inhibition of membrane and peptidoglycan synthesis pathways

  • Exploitation of potential synthetic lethality with other divisome components

• Species-Selective Targeting:

  • Focusing on unique structural features of VP1970 not present in mammalian proteins

  • Developing agents specific to pathogenic Vibrio species

  • Creating narrow-spectrum antibiotics with reduced impact on beneficial microbiota

• Anti-Virulence Strategies:

  • If VP1970 affects cell morphology without being essential, targeting it might reduce virulence

  • Modulation of bacterial cell division to promote immune clearance

  • Disruption of biofilm formation by interfering with proper cell division

The development pathway would require:

• Validation of essentiality in relevant pathogenic species

• High-throughput screening assays for inhibitor identification

• Medicinal chemistry optimization of hit compounds

• In vitro and in vivo efficacy and toxicity testing

This approach aligns with the urgent need for novel antibacterial targets to address the global challenge of antimicrobial resistance.

What emerging technologies might advance VP1970 research in the next decade?

Several emerging technologies are poised to significantly advance VP1970 research in the coming decade:

• Cryo-Electron Tomography:

  • Visualization of VP1970 in its native cellular context at near-atomic resolution

  • 3D mapping of divisome architecture during different stages of cell division

  • Correlation with fluorescence microscopy for protein identification

• Advanced Mass Spectrometry:

  • Native MS techniques for intact membrane protein complexes

  • Hydrogen-deuterium exchange with improved spatial resolution

  • Crosslinking MS for in situ interaction mapping

• Genome Engineering Technologies:

  • CRISPR-Cas systems adapted for precise bacterial genome editing

  • Base editing for generating point mutations without double-strand breaks

  • CRISPRi for temporary, tunable gene repression

• Single-Molecule Approaches:

  • Super-resolution microscopy combining protein tracking with structural imaging

  • Single-molecule FRET to detect conformational changes during function

  • Optical tweezers or atomic force microscopy to measure mechanical properties

• Artificial Intelligence Applications:

  • Deep learning for protein structure prediction based on limited experimental data

  • Network analysis for predicting functional relationships from large-scale datasets

  • Automated image analysis for high-throughput phenotypic screening

• Microfluidics and Lab-on-a-Chip:

  • Single-cell analysis of division processes in controlled environments

  • High-throughput screening of genetic or chemical perturbations

  • Real-time monitoring of division dynamics under changing conditions

• Synthetic Biology Tools:

  • Reconstitution of minimal division systems incorporating VP1970

  • Optogenetic control of protein activity with spatial and temporal precision

  • Cell-free expression systems for rapid protein production and testing

These emerging technologies will enable researchers to address previously intractable questions about VP1970's structure, dynamics, interactions, and functions, potentially revealing new principles of bacterial cell division and identifying novel approaches for antimicrobial intervention.