Recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH)

What is Renibacterium salmoninarum ATP synthase subunit delta (atpH) and what is its biological function?

Renibacterium salmoninarum ATP synthase subunit delta (atpH) is a component of the F-type ATP synthase complex, a critical enzyme involved in cellular energy metabolism. The delta subunit serves as part of the central stalk of the F1 sector of ATP synthase, connecting the catalytic F1 portion to the membrane-embedded F0 portion. This connection is crucial for the mechanical rotation that couples proton transport to ATP synthesis or hydrolysis.

In R. salmoninarum, ATP synthase is essential for energy production, particularly under the challenging environmental conditions the pathogen faces during infection. The protein has a full amino acid sequence of 271 amino acids as identified in R. salmoninarum strain ATCC 33209 / DSM 20767 / JCM 11484 / NBRC 15589 / NCIMB 2235 . The delta subunit has a particular significance in maintaining the structural integrity of the ATP synthase complex and ensuring efficient energy conversion.

What are the optimal storage conditions for recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH)?

For short-term storage, recombinant R. salmoninarum ATP synthase subunit delta (atpH) should be stored at -20°C, while for extended storage, conservation at -20°C or -80°C is recommended . Working aliquots can be maintained at 4°C for up to one week. The protein should be reconstituted in deionized sterile water to a concentration of 0.1-1.0 mg/mL.

To enhance stability during storage, it is advisable to add glycerol to a final concentration of 5-50%, with 50% being the standard recommendation for optimal preservation . Repeated freezing and thawing cycles should be avoided as they can compromise protein integrity and biological activity. The shelf life of the liquid form is typically around 6 months when stored at -20°C/-80°C, while the lyophilized form maintains stability for approximately 12 months under the same conditions .

How is recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH) typically expressed and purified?

Recombinant R. salmoninarum ATP synthase subunit delta (atpH) is typically expressed in yeast expression systems . This eukaryotic expression platform offers advantages for producing bacterial proteins with proper folding and minimal aggregation. The protein is expressed as the full-length sequence comprising amino acids 1-271, corresponding to the complete native protein.

For purification, standard chromatographic techniques are employed, typically involving affinity chromatography using tags determined during the manufacturing process. The purified protein typically achieves >85% purity as determined by SDS-PAGE analysis . The specific tag used for purification is determined during the production process and may vary between different manufacturers. After purification, the protein is typically stored in a Tris-based buffer with 50% glycerol to maintain stability. Similar buffer compositions are used for related ATP synthase components such as subunit b (atpF) .

How can recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH) be used in immunological studies?

Recombinant R. salmoninarum ATP synthase subunit delta (atpH) serves as a valuable tool in immunological research, particularly for understanding host-pathogen interactions during bacterial kidney disease (BKD). When using this protein for immunological studies, researchers should consider the following methodological approaches:

• Antibody Production and Validation: The purified recombinant protein (>85% purity) can be used as an immunogen to develop polyclonal or monoclonal antibodies. These antibodies can then be applied in immunoassays such as ELISA, Western blotting, or immunohistochemistry to detect the native protein in bacterial samples or infected tissues.

• T-cell Response Analysis: Researchers can employ the recombinant protein to stimulate leukocytes isolated from fish to evaluate T-cell proliferation and cytokine production. This approach helps characterize cell-mediated immune responses, which appear to be critical in R. salmoninarum infections, particularly at chronic infection stages (98 days post-infection) .

• Vaccination Studies: The protein can be evaluated as a subunit vaccine candidate, administered alone or in combination with adjuvants, to assess protective immunity against R. salmoninarum challenge. Based on studies of R. salmoninarum pathogenesis, researchers should monitor immune responses at both early (28 days) and chronic (98 days) timepoints post-immunization .

What experimental controls should be included when working with recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH)?

When designing experiments with recombinant R. salmoninarum ATP synthase subunit delta (atpH), proper controls are essential for result interpretation:

• Negative Controls:

  • Buffer-only treatments (e.g., PBS-T20) to establish baseline readings in immunoassays

  • Recombinant proteins from non-related bacterial species to confirm specificity of observed effects

  • In immunological studies, include samples from non-immunized or mock-immunized animals

• Positive Controls:

  • Other well-characterized R. salmoninarum antigens with known biological activities

  • Dilution series (1:10, 1:100, 1:1000) of positive antigen controls in immunoassays to generate standard curves

  • Known immunostimulants when evaluating immune responses

• Technical Validation Controls:

  • SDS-PAGE analysis to confirm protein purity (should be >85%)

  • Western blotting to verify protein identity using specific antibodies

  • Functional assays to confirm biological activity when applicable

• Experimental Design Considerations:

  • Include multiple time points for sampling (e.g., 28 and 98 days post-infection) based on known R. salmoninarum infection kinetics

  • Use appropriate statistical analysis methods (e.g., Program R) for data interpretation

How can recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH) be incorporated into diagnostic assays?

Recombinant R. salmoninarum ATP synthase subunit delta (atpH) can enhance the specificity and sensitivity of diagnostic assays for bacterial kidney disease (BKD). Implementation strategies include:

• ELISA-Based Detection:

  • The recombinant protein can serve as a coating antigen for indirect ELISA to detect antibodies against R. salmoninarum in fish serum

  • Alternatively, antibodies raised against the recombinant protein can be used to capture native atpH in direct sandwich ELISA

  • For optimal results, microplates should be prepared with appropriate washing steps and blocking agents to minimize non-specific binding

• Molecular Diagnostic Enhancement:

  • While isothermal amplification methods like recombinase polymerase amplification (RPA) coupled with CRISPR-Cas12a have been developed for R. salmoninarum detection with a limit of detection of approximately 20-40 copies/μL , incorporating atpH-specific primers or probes could further improve assay specificity

  • The atpH gene sequence can be targeted for development of specific PCR or isothermal amplification assays with appropriate controls to ensure specificity

• Immunochromatographic Testing:

  • Development of rapid field tests using atpH-specific antibodies conjugated to colored particles

  • Such assays would enable point-of-care testing in aquaculture facilities with minimal equipment requirements

• Multiplex Diagnostic Platforms:

  • Integration of atpH detection with other R. salmoninarum antigens to increase diagnostic confidence

  • Combination with detection systems for other salmonid pathogens for comprehensive health monitoring

What role might ATP synthase subunit delta (atpH) play in Renibacterium salmoninarum pathogenicity and host interaction?

While direct evidence for R. salmoninarum ATP synthase subunit delta (atpH) in pathogenicity is limited, several research approaches can investigate this question:

• Gene Expression Analysis:

  • RNA sequencing data indicates that R. salmoninarum causes immune suppression at 28 days post-infection (dpi) in lumpfish, while inducing a cell-mediated immune response at 98 dpi

  • Investigation of atpH expression under different infection conditions could reveal whether this gene is differentially regulated during pathogenesis

• Functional Significance:

  • ATP synthesis is crucial for bacterial survival during infection, especially under stress conditions

  • The formation of bacterial aggregates observed in R. salmoninarum cultures might protect the bacteria from environmental stressors and could involve energy-dependent processes regulated by ATP synthase activity

• Potential Research Directions:

  • Construction of atpH deletion or conditional mutants to evaluate growth, survival, and virulence in laboratory and fish infection models

  • Evaluation of atpH expression under different environmental conditions, including those mimicking host environments (e.g., different pH, temperature, nutrient availability)

  • Investigation of whether atpH or its products serve as pathogen-associated molecular patterns (PAMPs) recognized by the fish immune system

• Experimental Model Considerations:

  • Lumpfish models have shown typical BKD clinical signs with 35% mortality following R. salmoninarum infection

  • Studies should incorporate both early (28 dpi) and chronic (98 dpi) infection timepoints to capture the dynamic changes in host-pathogen interactions

How can structural analysis of recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH) inform drug discovery efforts against bacterial kidney disease?

Structural analysis of R. salmoninarum ATP synthase subunit delta (atpH) represents a promising approach for targeted drug discovery against bacterial kidney disease:

• Structural Characterization Methods:

  • X-ray crystallography or cryo-electron microscopy of the purified recombinant protein (>85% purity) can reveal detailed three-dimensional structure

  • NMR spectroscopy can provide insights into dynamic properties and ligand interactions

  • In silico molecular modeling based on the known amino acid sequence can predict structural features and potential binding sites

• Target Validation Approaches:

  • Site-directed mutagenesis of key residues identified through structural analysis

  • Assessment of protein-protein interactions within the ATP synthase complex

  • Evaluation of the impact of environmental conditions (pH, temperature) on protein structure and function, considering R. salmoninarum's survival characteristics in different aquatic environments

• Drug Discovery Applications:

  • Identification of unique structural features or binding pockets specific to R. salmoninarum atpH

  • Structure-based virtual screening to identify small molecule inhibitors

  • Development of peptidomimetic inhibitors targeting critical protein-protein interfaces

• Experimental Validation:

  • Biochemical assays to evaluate inhibitor binding and impact on ATP synthase function

  • Growth inhibition assays using identified compounds

  • Evaluation of compounds in infection models, considering the unique aspects of R. salmoninarum pathogenesis including its persistence in tissues for extended periods (up to 98 dpi)

What are the main technical challenges in working with recombinant Renibacterium salmoninarum ATP synthase subunit delta (atpH)?

Researchers working with recombinant R. salmoninarum ATP synthase subunit delta (atpH) face several technical challenges that require specific methodological solutions:

• Protein Stability Issues:

  • Challenge: The protein may exhibit limited stability during storage and experimental handling

  • Solution: Store at -20°C or -80°C with 50% glycerol as a cryoprotectant; avoid repeated freeze-thaw cycles; maintain working aliquots at 4°C for maximum one week

  • Validation: Monitor protein integrity by SDS-PAGE before experimental use

• Functional Assay Development:

  • Challenge: Establishing reliable assays to confirm biological activity of the recombinant protein

  • Solution: Develop ATP synthesis/hydrolysis assays using reconstituted systems or measure interaction with other ATP synthase components through co-immunoprecipitation or surface plasmon resonance

  • Controls: Include positive controls with known ATP synthase activity and negative controls with denatured protein

• Aggregation During Expression and Purification:

  • Challenge: Bacterial proteins often form inclusion bodies or aggregates during heterologous expression

  • Solution: Optimize expression conditions in yeast systems , consider fusion tags to enhance solubility, and employ appropriate detergents during purification if necessary

  • Quality control: Verify monodispersity through size exclusion chromatography or dynamic light scattering

• Cross-reactivity in Immunological Applications:

  • Challenge: Potential antigenic cross-reactivity with ATP synthase proteins from other bacteria

  • Solution: Conduct extensive specificity testing against related bacterial proteins; identify and focus on unique epitopes specific to R. salmoninarum atpH

  • Validation: Test antibody specificity against a panel of bacterial lysates from species commonly co-occurring with R. salmoninarum in aquatic environments

How can researchers optimize experimental protocols when studying the interactions between Renibacterium salmoninarum ATP synthase subunit delta (atpH) and the host immune system?

Optimizing experimental protocols for studying interactions between R. salmoninarum ATP synthase subunit delta (atpH) and host immune responses requires careful consideration of several factors:

• Protein Preparation for Immunological Studies:

  • Ensure endotoxin removal from recombinant protein preparations to prevent non-specific immune activation

  • Verify protein folding using circular dichroism or other structural analysis methods to confirm native-like conformation

  • Use freshly reconstituted protein at defined concentrations (0.1-1.0 mg/mL) for consistent results

• Fish Immune Cell Isolation and Culture:

  • Optimize methods for isolation of leukocytes from relevant tissues (head kidney, spleen) of target fish species

  • Develop appropriate cell culture conditions that maintain viability and functionality of fish immune cells

  • Include time course analyses to capture both early (28 dpi) and chronic (98 dpi) immune responses

• Gene Expression Analysis:

  • Design gene-specific primers for quantitative PCR targeting relevant immune markers

  • Consider whole transcriptome approaches (RNA-seq) to capture comprehensive immune responses

  • Apply appropriate normalization methods using validated reference genes for fish immunological studies

• Data Analysis and Interpretation:

  • Use appropriate statistical methods (e.g., Program R) for analyzing complex immunological data

  • Consider the natural variability in fish immune responses when determining sample sizes

  • Include proper controls for each experimental condition and technical replicates to ensure reproducibility

What are the best approaches for studying the ATP synthase complex structure in Renibacterium salmoninarum using recombinant subunits?

To elucidate the structure and function of the complete ATP synthase complex in R. salmoninarum using recombinant subunits, researchers should consider the following methodological approaches:

• Recombinant Expression of Multiple Subunits:

  • Express and purify multiple ATP synthase components including subunit delta (atpH) and subunit b (atpF)

  • Consider co-expression systems to facilitate proper assembly of subunit interactions

  • Design constructs with compatible affinity tags to enable purification of assembled subcomplexes

• Structural Analysis Techniques:

  • Cryo-electron microscopy (cryo-EM) for visualization of assembled complexes

  • X-ray crystallography for high-resolution structures of individual subunits or stable subcomplexes

  • Hydrogen-deuterium exchange mass spectrometry (HDX-MS) to map protein-protein interfaces

  • Crosslinking mass spectrometry to identify spatial relationships between subunits

• Functional Reconstitution:

  • Develop protocols for in vitro reconstitution of ATP synthase activity using purified recombinant subunits

  • Measure ATP synthesis/hydrolysis activities of reconstituted complexes under various conditions

  • Compare activities of wild-type complexes with those containing site-directed mutations in key residues

• Comparative Analysis with Model Organisms:

  • Leverage structural information from well-characterized ATP synthases from model organisms

  • Identify unique features of R. salmoninarum ATP synthase that might relate to its pathogenicity or environmental adaptation

  • Consider the habitat and infection biology of R. salmoninarum when interpreting structural features, particularly its ability to survive in various water conditions for extended periods

How might research on Renibacterium salmoninarum ATP synthase subunit delta (atpH) contribute to development of new vaccination strategies against bacterial kidney disease?

Research on R. salmoninarum ATP synthase subunit delta (atpH) offers several promising avenues for novel vaccination strategies against bacterial kidney disease:

• Subunit Vaccine Development:

  • The recombinant atpH protein (>85% purity) could serve as a subunit vaccine candidate

  • Experimental design should include dose-response studies and adjuvant optimization

  • Evaluation of protection should assess both early (28 dpi) and chronic (98 dpi) stages of infection, given the distinct immune responses observed at these timepoints

• Epitope Mapping and Peptide Vaccines:

  • Identification of immunodominant B-cell and T-cell epitopes within the 271-amino acid atpH sequence

  • Design of synthetic peptide vaccines targeting these epitopes

  • Evaluation of epitope conservation across R. salmoninarum strains to ensure broad protection

• DNA Vaccine Approaches:

  • Construction of DNA vaccines encoding atpH for in vivo expression

  • Optimization of promoter and codon usage for expression in fish cells

  • Assessment of cell-mediated immune responses, which appear particularly important in chronic R. salmoninarum infection

• Combinatorial Vaccine Strategies:

  • Integration of atpH with other R. salmoninarum antigens for broader protection

  • Consideration of riboflavin biosynthesis components as additional targets, given their importance for virulence in related pathogens

  • Development of multivalent vaccines that protect against multiple fish pathogens common in aquaculture settings

What novel detection methods could be developed targeting Renibacterium salmoninarum ATP synthase subunit delta (atpH) for early diagnosis of bacterial kidney disease?

The development of novel detection methods targeting R. salmoninarum atpH could significantly improve early diagnosis of bacterial kidney disease:

• Advanced Molecular Detection:

  • Design of isothermal amplification assays (similar to existing RPA methods) specifically targeting the atpH gene

  • Integration with CRISPR-Cas12a detection systems to achieve sensitivity comparable to or better than the current limit of detection of 20-40 copies/μL

  • Development of multiplexed assays that simultaneously detect multiple R. salmoninarum targets for increased confidence

• Biosensor Development:

  • Creation of aptamer-based biosensors targeting atpH protein

  • Development of field-deployable electrochemical sensors for on-site testing in aquaculture facilities

  • Engineering of colorimetric assays that can be interpreted without specialized equipment

• Environmental DNA (eDNA) Monitoring:

  • Optimization of water sample collection and processing methods for atpH detection

  • Development of quantitative assays that correlate environmental levels with infection risk

  • Implementation of monitoring programs that could detect R. salmoninarum before clinical signs appear, similar to existing approaches that can detect the pathogen in hatchery water samples

• Artificial Intelligence Integration:

  • Development of image analysis algorithms to identify subtle morphological changes in fish associated with early BKD

  • Creation of predictive models integrating multiple biomarkers including atpH detection

  • Implementation of automated monitoring systems for aquaculture facilities

How could comparative genomic and proteomic analyses of Renibacterium salmoninarum ATP synthase components across different strains inform our understanding of pathogen evolution and host adaptation?

Comparative genomic and proteomic analyses of R. salmoninarum ATP synthase components offer valuable insights into pathogen evolution and host adaptation:

• Strain Variation Analysis:

  • Sequence comparison of atpH and other ATP synthase genes across multiple R. salmoninarum strains, including reference strains like ATCC 33209 / DSM 20767 / JCM 11484 / NBRC 15589 / NCIMB 2235

  • Identification of conserved regions that may be essential for function versus variable regions that might reflect adaptation to different hosts or environments

  • Correlation of genetic variations with virulence differences observed between strains

• Evolutionary Analysis:

  • Phylogenetic comparison of ATP synthase components across related bacterial species

  • Identification of selection pressures acting on specific regions of the proteins

  • Analysis of horizontal gene transfer events that might have influenced ATP synthase evolution

• Host-Pathogen Co-evolution:

  • Comparison of R. salmoninarum ATP synthase components from isolates obtained from different fish species

  • Investigation of potential adaptations related to the thermal environments of different host species

  • Analysis of how ATP synthase components might have evolved in response to different host immune pressures

• Environmental Adaptation Signatures:

  • Examination of ATP synthase modifications that might contribute to the remarkable environmental persistence of R. salmoninarum in river water and groundwater

  • Investigation of how ATP synthase function might be maintained under the varying conditions encountered during the pathogen's lifecycle

  • Correlation of genetic variations with the ability of different isolates to form bacterial aggregates, which may protect against environmental stressors

How should researchers interpret experimental data when studying the immunological response to Renibacterium salmoninarum ATP synthase subunit delta (atpH)?

When interpreting experimental data related to immunological responses to R. salmoninarum ATP synthase subunit delta (atpH), researchers should consider several key factors:

• Temporal Dynamics of Immune Response:

  • Interpret results in the context of infection stage, recognizing the distinct phases observed in R. salmoninarum infections:

    • Early infection (28 dpi): Characterized by immune suppression

    • Chronic infection (98 dpi): Associated with cell-mediated immune responses

  • Consider that experimental timepoints should capture both phases for comprehensive understanding

• Fish Species Variation:

  • Different fish species show varying susceptibility to R. salmoninarum, with lumpfish exhibiting typical BKD clinical signs and 35% mortality

  • Data interpretation should account for species-specific immune responses and potential differences in recognition of bacterial antigens

• Data Normalization and Statistical Analysis:

  • Apply appropriate statistical methods (e.g., Program R) with consideration of biological variability

  • For gene expression studies, ensure proper normalization with validated reference genes

  • Consider both statistical significance and biological relevance when interpreting results

• Cross-reactivity Considerations:

  • Evaluate potential cross-reactivity of antibodies or cellular responses with homologous proteins from other bacteria

  • Include appropriate controls to distinguish specific responses to R. salmoninarum atpH from non-specific reactions

How can researchers effectively collaborate on studies involving Renibacterium salmoninarum ATP synthase subunit delta (atpH)?

Effective collaboration on R. salmoninarum ATP synthase subunit delta (atpH) research requires structured approaches to resource sharing, methodological standardization, and interdisciplinary integration:

• Reagent and Resource Sharing:

  • Establish repositories for sharing recombinant proteins, antibodies, and genetic constructs

  • Develop standardized protocols for protein expression, purification, and storage to ensure consistency across laboratories

  • Create well-characterized reference materials with defined properties (e.g., proteins with >85% purity by SDS-PAGE)

• Methodological Standardization:

  • Develop consensus protocols for key assays, such as:

    • Protein handling and reconstitution procedures

    • Immunological assays for detecting R. salmoninarum in fish tissues

    • Challenge models in different fish species with defined infection parameters

  • Establish reporting standards for experimental conditions and results to facilitate meta-analysis

• Interdisciplinary Collaboration Framework:

  • Integrate expertise from:

    • Structural biologists for protein characterization

    • Immunologists for host response studies

    • Aquaculture specialists for applied research

    • Computational biologists for sequence and structure analysis

  • Implement regular knowledge-sharing sessions to bridge disciplinary gaps

• Data Management and Integration:

  • Develop databases for R. salmoninarum research including sequence variations, experimental protocols, and results

  • Implement data standards that facilitate comparison across studies

  • Create visualization tools for complex datasets derived from transcriptomic or proteomic studies

What are the critical knowledge gaps in our understanding of Renibacterium salmoninarum ATP synthase components that future research should address?

Despite advances in R. salmoninarum research, several critical knowledge gaps remain regarding ATP synthase components:

• Structural Knowledge Gaps:

  • High-resolution structures of R. salmoninarum ATP synthase components, including atpH, are lacking

  • The specific interactions between subunits in the assembled complex remain poorly characterized

  • Structural adaptations that might enable function under various environmental conditions encountered during infection are unknown

• Functional Knowledge Gaps:

  • The precise role of ATP synthase in R. salmoninarum virulence remains unclear

  • Regulatory mechanisms controlling ATP synthase expression during different infection phases (early vs. chronic) are not well understood

  • The impact of environmental conditions (pH, temperature, nutrient availability) on ATP synthase function and its relation to bacterial survival in different water conditions requires further investigation

• Immunological Knowledge Gaps:

  • The immunogenicity of ATP synthase components in different fish species is poorly characterized

  • The potential of ATP synthase components as vaccine candidates has not been systematically evaluated

  • The role of host immune recognition of ATP synthase components in protection versus pathology remains unclear

• Applied Research Needs:

  • Development of targeted inhibitors specific to R. salmoninarum ATP synthase

  • Optimization of diagnostic assays incorporating ATP synthase detection for early BKD diagnosis

  • Evaluation of ATP synthase components in multivalent vaccine formulations for aquaculture

How can the study of Renibacterium salmoninarum ATP synthase subunit delta (atpH) contribute to broader understanding of bacterial bioenergetics in fish pathogens?

Research on R. salmoninarum ATP synthase subunit delta (atpH) offers valuable contributions to our broader understanding of bacterial bioenergetics in fish pathogens:

• Comparative Bioenergetics:

  • Comparison of ATP synthase structure and function across diverse fish pathogens

  • Investigation of how energy metabolism adaptations contribute to pathogen success in different ecological niches

  • Analysis of how ATP synthase modifications might contribute to the remarkable persistence of R. salmoninarum in aquatic environments for up to 14 weeks

• Environmental Adaptation Mechanisms:

  • Study of how ATP synthase function is maintained under changing environmental conditions in aquatic systems

  • Investigation of energy conservation strategies during nutrient limitation or stress conditions

  • Research on the role of ATP synthesis in bacterial aggregate formation , which may represent an energy-dependent adaptive response

• Host-Pathogen Energetic Interfaces:

  • Exploration of how bacterial energy metabolism interacts with host cellular processes during infection

  • Investigation of potential targeting of host energy resources by bacterial pathogens

  • Analysis of how immune recognition of bacterial ATP synthase components might influence infection outcomes

• Evolutionary Perspectives:

  • Comparison of ATP synthase components across evolutionary diverse fish pathogens

  • Identification of conserved features essential for function versus adaptable elements

  • Study of how ATP synthase evolution might parallel adaptation to different host species or environmental conditions