Recombinant Vibrio fischeri UPF0761 membrane protein VF_0100 (VF_0100)

What is Vibrio fischeri UPF0761 membrane protein VF_0100?

The UPF0761 membrane protein VF_0100 is a protein encoded by the Vibrio fischeri genome, specifically identified in strain ES114. It is a membrane-associated protein of 310 amino acids that belongs to the UPF0761 protein family, a group of uncharacterized proteins with conserved function prediction . The protein has been produced recombinantly with N-terminal His-tags to facilitate purification and subsequent analysis in laboratory settings . The protein's membrane localization suggests potential roles in cellular processes such as signaling, transport, or structural functions within the bacterial membrane system.

Why is Vibrio fischeri used as a model organism in research?

Vibrio fischeri serves as a valuable non-pathogenic model organism related to pathogenic Vibrio species. Its primary research significance lies in its well-characterized symbiotic relationship with the Hawaiian bobtail squid Euprymna scolopes . This symbiosis provides an excellent model for studying host-microbe interactions in a natural context. Additionally, V. fischeri offers high genetic tractability, making it amenable to various genetic manipulation techniques that allow researchers to investigate pathways mediating symbiotic interactions . The availability of complete genome sequences for multiple V. fischeri strains, including ES114 and MJ11, further enhances its utility as a model organism for comparative genomics and evolutionary studies .

What genetic manipulation techniques are available for studying V. fischeri proteins?

Several robust genetic manipulation techniques have been established for V. fischeri research:

• Transformation: Researchers can introduce linear DNA to create chromosomal mutations. This approach allows for targeted gene modifications including deletions, insertions, and point mutations .

• Conjugation: This method enables the introduction of plasmid DNA into V. fischeri, with subsequent protocols for eliminating unstable plasmids when necessary .

• Antibiotic resistance cassette manipulation: Specific antibiotic resistance cassettes designed for V. fischeri allow for selection of desired genetic modifications. The Flp-FRT system permits removal of these cassettes after selection, enabling sequential gene mutations without limitation by available resistance markers .

• Transposon mutagenesis: Both random and site-specific mutagenesis can be performed using transposons, providing versatility in generating V. fischeri mutants for functional studies .

These techniques collectively provide researchers with a comprehensive toolkit for investigating protein function, including membrane proteins like VF_0100.

What is known about the structure of UPF0761 membrane proteins?

Current structural knowledge of UPF0761 family membrane proteins, including VF_0100, remains limited. As a membrane protein, VF_0100 is predicted to contain hydrophobic transmembrane domains that anchor it within the bacterial cell membrane. While specific crystallographic or NMR structures for VF_0100 have not been widely reported, computational methods and comparative structural biology approaches can provide insights into potential structural features .

Recent advancements in computational design of membrane protein analogues demonstrate that membrane topologies can be recapitulated in solution, suggesting potential approaches for structural studies of proteins like VF_0100 . Computational deep learning pipelines have shown promise in designing complex folds and soluble analogues of integral membrane proteins, potentially offering new avenues for structural investigation of challenging membrane proteins like UPF0761 family members .

How can genomic sequence errors affect research on V. fischeri proteins like VF_0100?

Genomic sequence errors can significantly impact research on V. fischeri proteins, as demonstrated by comparative genomics studies between V. fischeri strains ES114 and MJ11. Analysis identified 82 loci in ES114 likely containing errors, with 75 confirmed errors requiring correction of 10,457 base pairs . These sequence inaccuracies can manifest as:

• Frameshift errors: The most common type of error, resulting in improper ORF calling that artificially splits single genes into multiple adjacent ORFs. This could directly affect identification and characterization of membrane proteins like VF_0100 .

• Insertion errors: Contrary to the assumption that insertions are rare in microbial genome assemblies, fourteen loci contained extraneous sequences exceeding 300 bp. These resulted from imperfect contig ends misassembled in tandem rather than as overlapping segments .

• Nonsense mutations: These can prematurely terminate protein sequences, creating pseudogenes where functional genes should exist .

For VF_0100 specifically, researchers should verify the sequence accuracy through:

• Comparison with orthologs in related V. fischeri strains

• PCR amplification and resequencing of the genomic region

• Assessment of predicted protein domain integrity

The table below summarizes examples of sequence errors identified in V. fischeri ES114 compared to MJ11:

What approaches are recommended for functional characterization of UPF0761 membrane proteins?

Functional characterization of UPF0761 membrane proteins like VF_0100 requires a multifaceted approach:

• Gene knockout and complementation studies: Generate deletion mutants of VF_0100 in V. fischeri using transformation techniques, followed by phenotypic analysis and complementation with functional copies to verify observed phenotypes . This approach can reveal the protein's role in bacterial physiology, symbiosis establishment, or stress response.

• Protein-protein interaction studies: Techniques such as bacterial two-hybrid systems, co-immunoprecipitation, or crosslinking approaches can identify interaction partners, providing functional context within cellular pathways.

• Solubilization and reconstitution experiments: For membrane proteins, functional characterization often requires extraction from the membrane using detergents, followed by reconstitution in proteoliposomes or nanodiscs to study transport or signaling activities.

• Computational deep learning approaches: Recent advances in computational design of soluble analogues of membrane proteins can be applied to UPF0761 family proteins. These soluble versions retain structural features of the membrane-bound originals while being more amenable to functional studies .

• Comparative genomics: Examining conservation patterns and genomic context across different bacterial species can provide indirect evidence of functional roles and evolutionary importance .

• Transcriptomic analysis: RNA-seq experiments comparing wild-type and VF_0100 mutant strains under various conditions can reveal regulatory networks and physiological processes influenced by this protein.

How can recombinant VF_0100 be efficiently expressed and purified for structural studies?

Efficient expression and purification of recombinant VF_0100 for structural studies presents several challenges due to its membrane localization. The following methodological approaches are recommended:

• Expression system selection:

  • E. coli-based systems with specialized strains (C41, C43) designed for membrane protein expression

  • Cell-free expression systems which can directly incorporate membrane proteins into nanodiscs or liposomes

  • V. fischeri-based homologous expression systems when heterologous expression proves challenging

• Optimization of expression conditions:

  • Reduced induction temperature (16-25°C) to slow protein synthesis and improve folding

  • Induction at higher cell densities (OD600 > 0.8) to maximize biomass before potentially toxic protein expression

  • Use of mild inducers (like rhamnose-inducible promoters) for titratable expression levels

  • Co-expression with chaperones to assist proper folding

• Purification strategy:

  • Membrane isolation through ultracentrifugation

  • Solubilization screening with diverse detergents (DDM, LMNG, GDN)

  • Immobilized metal affinity chromatography (IMAC) using the N-terminal His-tag

  • Size exclusion chromatography for final polishing and buffer exchange

• Alternative approaches:

  • Creation of soluble analogues through computational design methods as demonstrated for other membrane proteins

  • Fusion with solubility-enhancing partners (MBP, SUMO) with cleavable linkers

  • Incorporation of stabilizing mutations identified through directed evolution or computational prediction

• Quality control assessments:

  • SEC-MALS to verify monodispersity

  • Thermal stability assays using differential scanning fluorimetry

  • Circular dichroism to confirm secondary structure content

What computational tools are most effective for predicting the structure and function of UPF0761 family proteins?

For predicting the structure and function of UPF0761 family proteins like VF_0100, several computational approaches have demonstrated effectiveness:

• Deep learning structure prediction tools:

  • AlphaFold2 and RoseTTAFold provide remarkably accurate predictions of protein structures, even for previously challenging membrane proteins

  • Specific membrane protein-focused implementations that account for lipid bilayer environments provide enhanced accuracy for transmembrane regions

• Robust deep learning pipelines for membrane protein design:

  • Recent advances demonstrate successful design of complex folds and soluble analogues of integral membrane proteins

  • These techniques can recapitulate structural features of membrane proteins in solution, enabling functional studies

• Comparative genomics tools:

  • Multiple sequence alignment tools like MUSCLE and Clustal Omega for identifying conserved domains

  • Homology detection through HHpred or HMMER for detecting distant relationships

  • Genomic context analysis to identify functional associations through gene neighborhood analysis

• Transmembrane topology prediction:

  • TMHMM, TOPCONS, and Phobius for predicting transmembrane segments

  • SignalP for signal peptide prediction

  • CCTOP for consensus topology prediction combining multiple algorithms

• Functional prediction software:

  • InterProScan for integrated domain and functional site analysis

  • COFACTOR for enzyme classification and binding site prediction

  • 3DLigandSite for ligand binding site prediction based on structural information

The integration of these tools can provide comprehensive insights into the potential structure and function of UPF0761 family proteins, guiding experimental design for functional characterization.

What protocols are recommended for genetic manipulation of VF_0100 in Vibrio fischeri?

The genetic manipulation of VF_0100 in Vibrio fischeri can be accomplished through several well-established protocols:

• Transformation-based chromosomal mutation:

  • Design PCR primers to amplify flanking regions of VF_0100

  • Join these fragments with an antibiotic resistance cassette through overlap extension PCR

  • Introduce this linear DNA into competent V. fischeri cells

  • Select transformants on appropriate antibiotic media

  • Confirm successful recombination through PCR verification using primers that flank the recombination site

• Conjugation for plasmid introduction:

  • Clone VF_0100 (wild-type or modified versions) into appropriate shuttle vectors

  • Transform into E. coli donor strain (typically containing conjugative machinery)

  • Mix with V. fischeri recipient strain and incubate on non-selective media

  • Transfer to selective media containing appropriate antibiotics

  • Protocols exist for subsequently eliminating unstable plasmids when necessary

• Antibiotic resistance cassette management:

  • Multiple antibiotic resistance cassettes are available for V. fischeri

  • For creating multiple mutations, the Flp-FRT system allows removal of antibiotic resistance markers

  • This enables sequential mutations without limitation by available resistance markers

• Site-directed mutagenesis approaches:

  • For studying specific domains or residues within VF_0100

  • Can be implemented through PCR-based methods or recombination-based approaches

  • Mutations can be introduced directly on the chromosome or on plasmids for complementation studies

Each approach has specific advantages depending on the experimental goals, whether creating knockouts, introducing point mutations, or establishing complementation systems.

How can researchers assess the membrane localization and topology of VF_0100?

Assessing membrane localization and topology of VF_0100 requires specialized techniques that address the challenges of working with membrane proteins:

These complementary approaches provide a comprehensive assessment of VF_0100 localization and topological arrangement within the membrane.

What techniques can be used to investigate protein-protein interactions involving VF_0100?

Investigating protein-protein interactions involving membrane proteins like VF_0100 requires specialized approaches:

• Bacterial two-hybrid systems:

  • Membrane-specific variants like BACTH (Bacterial Adenylate Cyclase Two-Hybrid)

  • Split-ubiquitin systems adapted for bacterial membrane proteins

  • These methods allow screening of interaction partners in vivo

• Co-immunoprecipitation approaches:

  • Solubilize membranes with mild detergents to preserve protein-protein interactions

  • Immunoprecipitate VF_0100 using anti-His antibodies

  • Identify co-precipitating proteins through mass spectrometry

  • Validate with reciprocal pulldowns and controls for non-specific binding

• Chemical crosslinking coupled with mass spectrometry:

  • Treat intact cells or membrane preparations with crosslinkers

  • Purify VF_0100 complexes under denaturing conditions

  • Analyze crosslinked peptides by mass spectrometry

  • This can identify both stable and transient interaction partners

• Proximity labeling techniques:

  • Fuse VF_0100 to enzymes like BioID or APEX2

  • These enzymes biotinylate nearby proteins when activated

  • Purify biotinylated proteins and identify by mass spectrometry

  • Especially valuable for transient or weak interactions in native membrane environments

• Förster Resonance Energy Transfer (FRET):

  • Generate fluorescent protein fusions to VF_0100 and potential partners

  • Measure energy transfer as indicator of proximity

  • Can be performed in live bacteria to capture physiologically relevant interactions

• Surface Plasmon Resonance or Microscale Thermophoresis:

  • For in vitro validation and quantification of interactions

  • Requires purified VF_0100, typically in detergent micelles or nanodiscs

  • Provides binding constants and kinetic parameters

• Genetic interaction mapping:

  • Synthetic genetic arrays or transposon sequencing approaches

  • Identify genes that show epistatic relationships with VF_0100

  • These genetic interactions often reflect functional relationships or physical interactions

How does VF_0100 contribute to Vibrio fischeri symbiosis with its host?

While specific information about VF_0100's role in symbiosis is limited in the provided search results, we can outline a methodological approach to investigate this question:

• Symbiosis colonization assays:

  • Generate VF_0100 deletion mutants in V. fischeri

  • Assess colonization efficiency in the Hawaiian bobtail squid Euprymna scolopes model

  • Measure colonization levels at different time points using competitive indices against wild-type strains

  • Examine spatial distribution within the light organ using fluorescently labeled strains

• Host response analysis:

  • Compare host transcriptional responses to wild-type versus VF_0100 mutant strains

  • Assess morphological development of the light organ

  • Measure immune response markers in the presence of different bacterial strains

• Stress resistance profiling:

  • Test VF_0100 mutants for sensitivity to host-relevant stresses:

    • Oxidative stress (H₂O₂, hypochlorite)

    • Antimicrobial peptides

    • Osmotic stress conditions

  • These could reveal roles in surviving host defense mechanisms

• Comparative genomics approach:

  • Analyze conservation of VF_0100 across symbiotic versus non-symbiotic Vibrio species

  • Identify potential co-evolution patterns with host association

  • Examine genomic context for functional clues

• Metabolic profiling:

  • Compare metabolite utilization between wild-type and mutant strains

  • Assess changes in metabolic capabilities relevant to the symbiotic environment

  • Investigate whether VF_0100 influences utilization of host-derived nutrients

These systematic approaches would provide insights into whether and how VF_0100 contributes to the establishment and maintenance of the V. fischeri-squid symbiosis.

What is the potential for using computational design to create soluble analogues of VF_0100?

Recent advances in computational protein design offer promising avenues for creating soluble analogues of membrane proteins like VF_0100:

• Deep learning pipeline approach:

  • Robust deep learning methods have successfully designed complex folds and soluble analogues of integral membrane proteins

  • These approaches can recapitulate structural features of membrane proteins in solution

  • The resulting soluble analogues maintain high thermal stability and show remarkable design accuracy when compared to experimental structures

• Functional preservation strategies:

  • Soluble analogues can be functionalized with native structural motifs

  • This serves as proof of concept for transferring membrane protein functions to the soluble proteome

  • For VF_0100, key binding sites or catalytic regions could be preserved while redesigning the hydrophobic transmembrane regions

• Advantages for research applications:

  • Enhanced expression yields compared to membrane-bound versions

  • Simplified purification protocols without detergent requirements

  • Improved compatibility with structural biology techniques like X-ray crystallography

  • Potential for high-throughput screening applications

• Design considerations specific to UPF0761 family:

  • Identify conserved residues across the UPF0761 family that must be preserved

  • Determine which transmembrane regions can be replaced with soluble elements

  • Incorporate stabilizing interactions to compensate for the absence of membrane support

• Experimental validation pipeline:

  • Biophysical analyses to confirm thermal stability

  • Structural determination to verify design accuracy

  • Functional assays to assess preservation of native activities

This approach represents a potentially transformative strategy for studying membrane proteins like VF_0100, potentially enabling new approaches in understanding their function and developing applications in biotechnology and drug discovery .

How can the study of VF_0100 benefit from comparative genomics approaches?

Comparative genomics provides powerful insights for studying proteins like VF_0100:

• Sequence verification and error correction:

  • Comparison between V. fischeri strains (such as ES114 and MJ11) can identify potential sequencing errors

  • This approach revealed 82 loci with likely errors in ES114, leading to correction of 10,457 base pairs

  • Such corrections are critical for accurate annotation and functional characterization

• Evolutionary conservation analysis:

  • Comparison across diverse Vibrio species and beyond can reveal conserved domains

  • Conservation patterns often highlight functionally important regions

  • Variably conserved regions may indicate host-specific adaptations

• Genomic context examination:

  • Analysis of gene neighborhoods can reveal functional associations

  • Co-occurrence patterns across genomes suggest functional relationships

  • Operonic structures provide clues about coordinated expression and related functions

• Identification of paralogs and orthologs:

  • Distinguishing between paralogs (resulting from gene duplication) and orthologs (resulting from speciation)

  • This classification helps in transferring functional annotations from better-characterized proteins

  • Reciprocal BLAST analyses between strains like ES114 and MJ11 can identify true orthologs

• Detection of horizontal gene transfer:

  • Analysis of GC content, codon usage, and phylogenetic incongruence

  • Helps determine if VF_0100 was acquired through horizontal transfer

  • Provides insights into the evolutionary history and potential specialized functions

• Structural prediction refinement:

  • Multiple sequence alignments improve accuracy of structural predictions

  • Coevolution analysis can identify residues that interact in the three-dimensional structure

  • Conservation mapping onto predicted structures highlights functionally important surfaces

This multifaceted comparative genomics approach provides a robust framework for understanding VF_0100's evolution, function, and structural organization.

What are the key challenges and future directions in researching VF_0100 and similar membrane proteins?

Research on VF_0100 and similar membrane proteins faces several key challenges with corresponding future directions:

• Structural characterization challenges:

  • Membrane proteins remain difficult to crystallize for X-ray crystallography

  • Future directions include leveraging advances in cryo-EM for membrane proteins and computational approaches for structure prediction and design

  • Development of soluble analogues represents a promising strategy to overcome structural determination barriers

• Functional annotation limitations:

  • The UPF0761 family remains poorly characterized functionally

  • Future research should employ comprehensive phenotypic screening of deletion mutants

  • Multi-omics approaches combining transcriptomics, proteomics, and metabolomics will provide integrated functional insights

• Technical difficulties in genetic manipulation:

  • While V. fischeri is genetically tractable, membrane protein studies present specific challenges

  • Continued refinement of genetic tools specifically optimized for membrane protein manipulation will accelerate progress

  • CRISPR-Cas9 adaptation for Vibrio species offers opportunities for more precise genetic engineering

• Integration with symbiosis research:

  • Connecting molecular mechanisms to ecological functions remains challenging

  • Development of high-throughput colonization assays will enable more systematic screening

  • Advanced imaging techniques for visualizing protein localization during symbiosis establishment represent an important future direction

• Translation to biotechnological applications:

  • Moving from basic characterization to application development

  • Potential applications in biosensors, synthetic biology, and drug discovery platforms

  • Computational design of soluble analogues with preserved or enhanced functions offers exciting possibilities