Recombinant Klebsiella pneumoniae subsp. pneumoniae UPF0761 membrane protein KPN78578_41360 (KPN78578_41360)

What is Klebsiella pneumoniae UPF0761 membrane protein KPN78578_41360?

Klebsiella pneumoniae UPF0761 membrane protein KPN78578_41360 is a full-length (286 amino acids) transmembrane protein found in Klebsiella pneumoniae subsp. pneumoniae strain ATCC 700721/MGH 78578. It belongs to the UPF0761 protein family and has the UniProt ID A6TG76. The protein is typically produced as a recombinant protein with an N-terminal histidine tag expressed in E. coli expression systems for research purposes . Its complete amino acid sequence is: MLKTVHQKLLHHTRPLLAWLKLLWRRIDEDHMTTLAGNLAYVSLLSLVPLIAVVFALFAAFPMFSEVSVQIRHFIFANFIPATGDVIQGYIEQFVANSSRMTAVGAFGLIVTSLLLMYSIDSALNTIWRSTRSRPKVYSFAVYWMILTLGPLLAGASLAISSYLLSLRWASDLDGVIDNLLRLFPLILSWAAFWLLYSIVPTTQVRNRDAVIGALVAALLFEAGKKAFALYITTFPSYQLIYGVISVVPILFVWVYWTWCIVLLGAEITVTLGEYRKLKTEETEQP .

How conserved is this protein across different Klebsiella pneumoniae strains?

The UPF0761 membrane protein is highly conserved across different Klebsiella pneumoniae strains, as evidenced by the similar protein found in Klebsiella pneumoniae strain 342 (UniProt ID B5XZI5). The amino acid sequence comparison shows minimal variations between strains. For example, the KPK_5501 variant from strain 342 has a sequence of MLKTVQQKLHHHTRPLLAWLKLLWRRIDEDHMTTLAGNLAYVSLLSLVPLIAVVFALFAAFPMFSEVSVQIRHFIFANFIPATGDVIQGYIEQFVANSSRMTAVGAFGLIVTSLLLMYSIDSALNTIWRSTRSRPKVYSFAVYWMILTLGPLLAGASLAISSYLLSLRWASDLDGVIDNLLRLFPLILSWAAFWLLYSIVPTTQVRNRDAVIGALVAALLFEAGKKAFALYITTFPSYQLIYGVISVVPILFVWVYWTWCIVLLGAEITVTLGEYRKLKTEETEQP, which differs only slightly from the KPN78578_41360 variant . This high conservation suggests important functional roles and potential as a pan-strain vaccine candidate or diagnostic target.

What are the optimal storage and handling conditions for this recombinant protein?

For optimal preservation of protein integrity and activity, recombinant KPN78578_41360 is typically supplied in lyophilized form and should be stored at -20°C/-80°C. After reconstitution, working aliquots can be stored at 4°C for up to one week, but repeated freeze-thaw cycles should be avoided as they can compromise protein stability .

For reconstitution, it is recommended to briefly centrifuge the vial before opening to bring contents to the bottom. The protein should be reconstituted in deionized sterile water to a concentration of 0.1-1.0 mg/mL. For long-term storage, addition of 5-50% glycerol (final concentration) is recommended before aliquoting and storing at -20°C/-80°C . Generally, the shelf life of liquid form is approximately 6 months, while lyophilized form can remain stable for up to 12 months when stored properly .

What are the potential immunological applications of KPN78578_41360?

Based on research with similar outer membrane proteins from Klebsiella pneumoniae, membrane proteins have demonstrated significant potential as vaccine candidates. Studies have shown that certain outer membrane proteins can elicit strong antigen-specific IgG, IgG1, and IgG2a responses when used as immunogens . Although KPN78578_41360 has not been specifically identified among the protective antigens in the cited research, its characteristics as a conserved membrane protein make it a candidate worthy of investigation for vaccine development.

The research methodology for assessing immunological potential typically involves:

• Vaccination of mice with the purified recombinant protein

• Measurement of antigen-specific antibody responses (IgG, IgG1, IgG2a)

• Analysis of T-cell responses through ELISpot assays measuring IFN-γ-, IL-4-, and IL-17A-secreting splenocytes

• Evaluation of protective efficacy through infection models

• Assessment of opsonophagocytosis facilitation

How can researchers effectively study the structure-function relationship of this membrane protein?

Studying structure-function relationships of KPN78578_41360 presents challenges common to membrane proteins. A comprehensive approach would include:

• Bioinformatic analysis to predict transmembrane domains and topology

• Site-directed mutagenesis of key residues followed by functional assays

• Structural characterization through techniques such as:

  • X-ray crystallography (requiring detergent solubilization and crystallization)

  • Cryo-electron microscopy

  • NMR spectroscopy for dynamic studies

  • Molecular dynamics simulations to predict conformational changes

When designing such experiments, researchers should consider the hydrophobic nature of the protein, which contains multiple predicted transmembrane domains. The amino acid sequence suggests seven potential transmembrane segments with hydrophobic regions characteristic of integral membrane proteins .

What role might KPN78578_41360 play in antimicrobial resistance?

Given that Klebsiella pneumoniae is increasingly associated with antibiotic resistance, the potential role of membrane proteins in resistance mechanisms merits investigation. Research approaches could include:

• Comparative expression analysis between resistant and susceptible strains

• Gene knockout or knockdown studies to assess changes in antibiotic susceptibility

• Protein interaction studies to identify binding partners involved in efflux or membrane permeability

• Testing whether antibodies against the protein can restore antibiotic sensitivity

The K. pneumoniae 260 strain mentioned in the literature is resistant to multiple antibiotics including Amikacin, Cefuroxime-Sodium, Ciprofloxacin, and Piperacillin , making it a relevant model for such studies.

What expression systems are optimal for producing functional KPN78578_41360?

The recombinant KPN78578_41360 protein is typically expressed in E. coli expression systems with an N-terminal histidine tag to facilitate purification . This approach has proven effective for producing sufficient quantities for research purposes.

For researchers seeking to optimize expression, consider the following:

• Expression strain selection: BL21(DE3) or similar strains designed for membrane protein expression

• Induction conditions: Lower temperatures (16-25°C) often improve proper folding of membrane proteins

• Media optimization: Use of enhanced media formulations such as Terrific Broth or auto-induction media

• Detergent screening: Systematic testing of different detergents for optimal solubilization

Alternative expression systems such as yeast (Pichia pastoris) or insect cells might be considered for proteins requiring complex folding or post-translational modifications, though these have not been specifically reported for KPN78578_41360 in the available literature.

What purification strategies are most effective for this membrane protein?

Based on the available information, purification of recombinant KPN78578_41360 typically involves:

• Immobilized metal affinity chromatography (IMAC): Utilizing the N-terminal histidine tag for initial capture

• Buffer optimization: Including appropriate detergents to maintain protein solubility

• Purity assessment: SDS-PAGE analysis to confirm >85-90% purity

How can researchers assess the functional integrity of purified KPN78578_41360?

Assessing functional integrity is crucial but challenging for membrane proteins with poorly characterized functions like KPN78578_41360. Recommended approaches include:

• Circular dichroism (CD) spectroscopy: To confirm secondary structure elements characteristic of membrane proteins

• Size exclusion chromatography: To verify monodispersity and absence of aggregation

• Thermal shift assays: To assess protein stability under various conditions

• Reconstitution into liposomes: To evaluate membrane integration

• Binding assays: If ligands or interaction partners are identified

Additionally, for proteins intended for immunological studies, researchers should verify immunoreactivity through ELISA or Western blot using sera from infected hosts or specific antibodies if available.

What is the potential of KPN78578_41360 as a vaccine candidate?

While KPN78578_41360 has not been specifically evaluated as a vaccine candidate in the provided literature, research on other outer membrane proteins of Klebsiella pneumoniae provides valuable insights. Similar proteins (Kpn_Omp001, Kpn_Omp002, and Kpn_Omp005) have demonstrated promising results as vaccine candidates .

To evaluate KPN78578_41360 as a vaccine candidate, researchers should consider:

• Conservation analysis: Determine sequence conservation across clinical isolates

• Immunogenicity testing: Assess ability to stimulate both humoral and cellular immune responses

• Protection studies: Evaluate protective efficacy in appropriate animal models

• Mechanism investigation: Determine whether protection is mediated through:

  • Neutralizing antibodies

  • Opsonophagocytic activity

  • T-cell mediated immunity

The "shaving" proteomics approach described in the literature, which involves surface digestion of live bacterial cells followed by LC-MS/MS analysis, could be particularly valuable for identifying exposed epitopes of KPN78578_41360 that might be targeted by antibodies .

What techniques are effective for studying immune responses to KPN78578_41360?

Based on methodologies described for similar proteins, effective techniques for studying immune responses include:

• Antibody response analysis:

  • ELISA for measuring antigen-specific IgG, IgG1, and IgG2a titers

  • Western blotting for confirming antibody specificity

• T-cell response assessment:

  • ELISpot assays to quantify IFN-γ-, IL-4-, and IL-17A-secreting splenocytes

  • Flow cytometry to characterize T-cell subpopulations

  • Cytokine profiling to determine Th1/Th2/Th17 balance

• Functional immune assays:

  • Opsonophagocytosis assays using the protein-specific antisera

  • Complement-mediated killing assays

  • Neutralization assays if functional attributes are identified

• In vivo protection studies:

  • Challenge models with clinically relevant K. pneumoniae strains

  • Monitoring bacterial burden in tissues

  • Survival analysis

What are the main challenges in working with KPN78578_41360 and how can they be addressed?

Working with membrane proteins like KPN78578_41360 presents several technical challenges:

• Solubility issues:

  • Solution: Screen multiple detergents (CHAPS, DDM, OG, etc.) for optimal solubilization

  • Alternative: Consider membrane mimetics like nanodiscs or amphipols

• Protein degradation:

  • Solution: Include protease inhibitors during purification

  • Solution: Optimize buffer conditions (pH, salt concentration, additives)

• Low expression yields:

  • Solution: Codon optimization for expression host

  • Solution: Use specialized strains designed for membrane protein expression

  • Solution: Consider fusion partners that enhance solubility (MBP, SUMO, etc.)

• Proper folding:

  • Solution: Expression at lower temperatures (16-25°C)

  • Solution: Co-expression with chaperones

  • Solution: Addition of specific lipids during purification

• Functional characterization:

  • Solution: Collaborative approaches combining structural, biochemical, and computational methods

  • Solution: Homology-based functional prediction followed by targeted assays

How can researchers integrate bioinformatic and proteomic approaches to study KPN78578_41360?

The integration of bioinformatics and proteomics offers powerful approaches to studying proteins like KPN78578_41360:

• Sequence-based predictions:

  • Transmembrane topology prediction using tools like TMHMM or Phobius

  • Identification of conserved domains or motifs

  • Prediction of post-translational modifications

• Structural modeling:

  • Homology modeling based on related structures

  • Ab initio modeling of transmembrane regions

  • Molecular dynamics simulations to study dynamics

• Proteomics integration:

  • "Shaving" proteomics to identify surface-exposed regions

  • Cross-linking mass spectrometry to identify interaction partners

  • Comparative proteomics between strains or conditions

As described in the literature, the combination of surface "shaving" proteomics with bioinformatic prediction of surface proteins has been successful in identifying vaccine candidates for K. pneumoniae . This approach could be directly applied to further characterize KPN78578_41360.