Recombinant Laribacter hongkongensis Probable intracellular septation protein A (LHK_01701)

What is LHK_01701 and what is its basic function?

LHK_01701 is a probable intracellular septation protein A found in Laribacter hongkongensis. This protein is also known as YciB or an inner membrane-spanning protein . As suggested by its name, it likely plays a role in cellular septation, a critical process during bacterial cell division. The protein consists of 178 amino acids and contains transmembrane domains that anchor it to the bacterial inner membrane . The specific molecular mechanisms of its function in L. hongkongensis have not been fully characterized, but based on homologous proteins in other bacteria, it likely participates in coordinating cell division processes by facilitating proper septum formation during bacterial binary fission.

What is the amino acid sequence and structural characteristics of LHK_01701?

The full amino acid sequence of LHK_01701 is: MKFLSDLLPVLLFFAAYSLTGNIYLATGVAIVSTAAQVGISWFKHRKVEPMQWVSLALILVLGGLTLVLHDKRFIMWKPTVLYWLLGAGFLISDLAFRKNPIKAMMGKQIELPERLWAKLTFAWSGFFAFMGALNLFVAFNFSEAVWVNFKLFGGMGLMLVFVLAQGMVLSRYIQEKN . This 178-amino acid sequence features multiple hydrophobic regions, consistent with its predicted role as a membrane-spanning protein. Analysis of the sequence reveals multiple transmembrane domains, which anchor the protein to the bacterial inner membrane. The protein's hydrophobic character is evidenced by stretches of amino acids like leucine (L), isoleucine (I), valine (V), and phenylalanine (F), which are prevalent throughout the sequence, particularly in segments predicted to traverse the lipid bilayer.

What is known about Laribacter hongkongensis as the source organism?

Laribacter hongkongensis represents a novel bacterial genus and species that was first isolated in 2001 from the blood and empyema pus of a patient with alcoholic cirrhosis in Hong Kong . Subsequently, it has been isolated from patients in other parts of the world . This bacterium has been clinically associated with community-acquired gastroenteritis and traveler's diarrhea . Epidemiological studies have shown a significant association between consumption of freshwater fish and L. hongkongensis infection, with freshwater fish serving as a natural reservoir for this organism . Genotypic typing studies have revealed the possibility of virulent clones of L. hongkongensis, suggesting differential pathogenicity among strains . The bacterium possesses a class C beta-lactamase that has been cloned and characterized, which contributes to its antibiotic resistance profile .

What expression systems are most effective for producing recombinant LHK_01701?

For recombinant expression of LHK_01701, E. coli has been demonstrated as an effective heterologous host system . When expressing LHK_01701 in E. coli, the addition of an N-terminal His-tag has proven successful for subsequent purification steps . The full-length protein (all 178 amino acids) has been successfully expressed, suggesting that despite being a membrane protein, it can be produced recombinantly without significant toxicity to the host cells .

For optimal expression, researchers should consider:

• Codon optimization for E. coli if expression yields are suboptimal

• Induction conditions (temperature, inducer concentration, and duration)

• Cell lysis methods appropriate for membrane proteins

• Solubilization strategies using appropriate detergents if the protein aggregates in inclusion bodies

While E. coli is the documented expression system, researchers working with membrane proteins might also consider alternative systems such as Pichia pastoris for proteins that prove difficult to express functionally in prokaryotic systems.

What are the recommended storage and handling conditions for recombinant LHK_01701?

The recombinant LHK_01701 protein is typically provided as a lyophilized powder . For optimal stability and activity, the following storage and handling recommendations should be followed:

• Store the lyophilized powder at -20°C/-80°C upon receipt .

• Prior to opening, briefly centrifuge the vial to bring contents to the bottom .

• Reconstitute the protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL .

• After reconstitution, add glycerol to a final concentration of 5-50% (with 50% being the typical recommendation) for long-term storage at -20°C/-80°C .

• Aliquot the reconstituted protein to avoid repeated freeze-thaw cycles, as these are not recommended and can lead to protein degradation .

• Working aliquots can be stored at 4°C for up to one week .

• The storage buffer typically consists of a Tris/PBS-based buffer containing 6% trehalose at pH 8.0 .

These conditions are designed to maintain protein stability while minimizing degradation, aggregation, and loss of biological activity.

What methodologies can be employed to study LHK_01701's role in bacterial septation?

To investigate LHK_01701's role in bacterial septation, researchers should consider a multi-faceted experimental approach:

• Gene Knockout Studies: Generate LHK_01701 deletion mutants in L. hongkongensis and observe changes in cell morphology, division rates, and septum formation. Complementation with the wild-type gene would confirm phenotypic specificity.

• Localization Studies: Employ fluorescence microscopy with GFP-tagged LHK_01701 to visualize its subcellular localization during different stages of the cell cycle. Time-lapse imaging would reveal dynamic localization patterns during septation.

• Protein-Protein Interaction Analysis: Use techniques such as bacterial two-hybrid systems, co-immunoprecipitation, or pull-down assays to identify interaction partners of LHK_01701 . This would help establish its position in the septal protein interaction network.

• Structural Biology Approaches: While challenging for membrane proteins, techniques like X-ray crystallography or cryo-electron microscopy could provide insights into LHK_01701's structure and potential mechanistic function.

• In vitro Reconstitution Systems: Develop liposome-based systems incorporating purified LHK_01701 to study its effects on membrane dynamics and potential membrane-remodeling activities.

• Comparative Genomics: Analyze homologs of LHK_01701 in other bacterial species where septation mechanisms are better characterized to infer potential functional conservation.

• Transcriptomic and Proteomic Analysis: Compare wild-type and LHK_01701 mutant strains to identify dysregulated pathways that might reveal the protein's broader functional context.

These methodologies would collectively provide a comprehensive understanding of LHK_01701's role in bacterial septation beyond simple descriptive observations.

How might LHK_01701 contribute to L. hongkongensis pathogenicity?

The potential contribution of LHK_01701 to L. hongkongensis pathogenicity can be approached through several investigative avenues:

• Virulence in Infection Models: Compare the virulence of wild-type L. hongkongensis with LHK_01701 deletion mutants in appropriate animal or cell culture models. If septation is impaired, altered bacterial morphology might affect host-pathogen interactions, immune recognition, or antibiotic susceptibility.

• Stress Response Role: Examine whether LHK_01701 functions in bacterial adaptation to host-specific stresses (pH changes, nutrient limitation, host defense peptides) that would be encountered during infection.

• Cell Division Under Host Conditions: Determine if LHK_01701's septation function is particularly important under specific host-mimicking conditions, which might explain its potential role in pathogenicity.

• Association with Virulent Clones: Investigate whether genetic variations in LHK_01701 correlate with the "virulent clones" of L. hongkongensis that have been suggested by genotypic typing studies .

• Biofilm Formation: Assess whether LHK_01701 influences biofilm formation capacity, which is often associated with bacterial persistence and antibiotic resistance during infection.

• Host Cell Adhesion and Invasion: Determine if alterations in cell morphology due to LHK_01701 disruption affect the bacterium's ability to adhere to or invade host epithelial cells.

• Immune Evasion: Investigate whether LHK_01701's role in determining cell size and shape affects recognition by the host immune system or survival within phagocytes.

Understanding these aspects would provide insights into whether LHK_01701 directly contributes to pathogenicity or indirectly influences virulence through its fundamental role in bacterial cell division.

What techniques can be employed to study membrane protein-protein interactions involving LHK_01701?

Studying membrane protein-protein interactions presents unique challenges due to the hydrophobic nature of these proteins. For LHK_01701, researchers can employ:

• Bacterial Two-Hybrid Systems: Modified to accommodate membrane proteins, these systems can screen for potential interaction partners in a relatively high-throughput manner while maintaining proteins in their native membrane environment.

• Split GFP Complementation: By tagging LHK_01701 and potential partners with complementary GFP fragments, interactions can be visualized in living cells when proximity brings the fragments together to form a functional fluorophore.

• FRET/BRET Analyses: Förster/Bioluminescence Resonance Energy Transfer can detect protein-protein interactions within nanometer distances, suitable for membrane proteins labeled with appropriate donor/acceptor pairs.

• Co-immunoprecipitation with Membrane-Compatible Detergents: Using detergents that maintain native protein folding and interactions, pull-down assays can identify stable interaction partners.

• Cross-linking Mass Spectrometry: Chemical cross-linking followed by mass spectrometry can identify proteins in close proximity to LHK_01701 in the native membrane.

• Proximity Labeling Techniques: Methods like BioID or APEX2, where LHK_01701 is fused to a proximity-dependent labeling enzyme, can identify proteins in its vicinity within the membrane.

• Surface Plasmon Resonance: For purified proteins, SPR can quantify binding affinities between LHK_01701 and potential partners.

• Native PAGE Analysis: Blue native PAGE can preserve protein complexes during separation, allowing identification of LHK_01701-containing complexes.

Each technique has advantages and limitations, and complementary approaches should be employed to build a comprehensive interaction network for LHK_01701.

How can quasi-experimental designs be applied to study the clinical relevance of LHK_01701?

Quasi-experimental designs can be valuable for studying the clinical relevance of LHK_01701 when randomized controlled trials are not feasible for ethical or practical reasons . These approaches might include:

• Nonequivalent Groups Design: Comparing clinical outcomes between patients infected with L. hongkongensis strains expressing different variants or levels of LHK_01701 . While groups would not be randomly assigned, researchers could attempt to control for confounding variables through statistical methods.

• Regression Discontinuity Approach: If a quantifiable threshold in LHK_01701 expression or mutation status exists that might affect clinical outcomes, researchers could compare patients just above and below this threshold, where differences would be minimal except for the factor of interest .

• Natural Experiments: Taking advantage of situations where patients are exposed to different L. hongkongensis strains (with variations in LHK_01701) through random or random-like assignment by external factors, such as geographical location or timing of outbreaks .

• Time-Series Designs: Studying changes in clinical outcomes before and after the emergence of particular L. hongkongensis strains with altered LHK_01701 properties.

• Case-Control Studies: Comparing LHK_01701 characteristics in L. hongkongensis isolates from patients with severe versus mild disease.

These quasi-experimental approaches would enable researchers to study the clinical relevance of LHK_01701 while acknowledging the limitations in establishing direct causality compared to true experimental designs .

What is the epidemiological significance of L. hongkongensis and potential implications for LHK_01701 research?

The epidemiological profile of L. hongkongensis provides important context for LHK_01701 research:

These epidemiological aspects highlight the importance of studying L. hongkongensis proteins, including LHK_01701, in the context of both basic bacterial physiology and human disease.

What genomic and proteomic approaches would advance understanding of LHK_01701 function?

Advanced genomic and proteomic approaches could significantly enhance our understanding of LHK_01701:

• Comparative Genomics: Analyzing LHK_01701 homologs across bacterial species to identify conserved domains and evolutionary patterns that might reveal functional importance.

• Transcriptomic Profiling: RNA-seq analysis comparing wild-type and LHK_01701 mutant strains under various conditions to identify genes differentially expressed, potentially revealing pathways influenced by this protein.

• Ribosome Profiling: Determining if LHK_01701 expression or mutation affects translation of specific mRNAs, particularly those encoding other cell division proteins.

• Chromatin Immunoprecipitation (ChIP-seq): If LHK_01701 has any DNA-binding capacity or influences proteins that regulate gene expression, ChIP-seq could identify genomic binding sites.

• Quantitative Proteomics: Methods like SILAC (Stable Isotope Labeling with Amino acids in Cell culture) or TMT (Tandem Mass Tag) labeling to compare protein abundance profiles between wild-type and LHK_01701 mutant bacteria.

• Phosphoproteomics: Investigating whether LHK_01701 is post-translationally modified by phosphorylation or affects phosphorylation states of other proteins.

• Protein-Lipid Interaction Analysis: Techniques like lipidomics coupled with protein analysis to determine if LHK_01701 interacts with specific membrane lipids that might influence septation processes.

• Single-Cell Approaches: Technologies that examine gene expression or protein localization at the single-cell level to capture heterogeneity in LHK_01701 function across bacterial populations.

These approaches would collectively provide a systems-level understanding of LHK_01701's role in L. hongkongensis physiology and potentially pathogenicity.

How might structural biology approaches inform therapeutic targeting of LHK_01701?

Structural biology approaches could provide crucial insights for potential therapeutic targeting of LHK_01701:

• X-ray Crystallography/Cryo-EM: Determining the three-dimensional structure of LHK_01701 would reveal binding pockets or functional domains that could be targeted by small molecule inhibitors.

• NMR Spectroscopy: For specific domains or peptide fragments of LHK_01701, NMR could provide dynamic information about protein motion and ligand binding.

• Molecular Dynamics Simulations: Computational approaches to model LHK_01701's behavior in membrane environments and its interactions with other molecules, helping identify potential druggable sites.

• Structure-Based Drug Design: Using resolved structures to computationally screen or design compounds that could specifically bind to and inhibit LHK_01701 function.

• Hydrogen-Deuterium Exchange Mass Spectrometry: To identify regions of LHK_01701 involved in protein-protein interactions that could be targeted by peptide-based inhibitors.

• Fragment-Based Drug Discovery: Testing libraries of small molecular fragments for binding to purified LHK_01701, which could be developed into higher-affinity inhibitors.

• Epitope Mapping: Identifying surface-exposed regions of LHK_01701 that could be targeted by antibodies as potential therapeutic agents.

If LHK_01701 proves essential for L. hongkongensis viability or virulence, these structural approaches could support development of targeted antimicrobials with potentially narrow spectrum activity against this pathogen.