Recombinant Pseudoalteromonas atlantica ATP synthase subunit a (atpB)

How does atpB differ functionally from other ATP synthase subunits in Pseudoalteromonas species?

The atpB gene encodes the ATP synthase subunit a (also called F-ATPase subunit 6), which is functionally distinct from other subunits in the ATP synthase complex. While the F₁ domain (containing α and β subunits) exhibits catalytic activity for ATP synthesis, the atpB subunit is part of the membrane-embedded F₀ domain that forms the proton channel .

In Pseudoalteromonas, atpB plays a crucial role in establishing the proton gradient necessary for ATP synthesis. Unlike the rotating c-ring oligomer of the F₀ domain, the a-subunit (atpB) remains stationary during proton translocation. The interaction between the a-subunit and the c-ring is essential for proton movement across the membrane, which drives the rotation of the central stalk and consequently the conformational changes in F₁ domain necessary for ATP synthesis .

What are the known synonyms and identifiers for this protein?

The Pseudoalteromonas atlantica ATP synthase subunit a is known by several synonyms and identifiers in scientific databases and literature:

This standardized nomenclature allows researchers to accurately identify and reference this protein across different research platforms and databases .

What are the optimal storage and reconstitution conditions for recombinant P. atlantica atpB protein?

For optimal preservation of recombinant P. atlantica atpB protein activity, the following storage and reconstitution protocols are recommended:

Storage Protocol:

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

• Aliquot the reconstituted protein to avoid repeated freeze-thaw cycles

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

• Long-term storage requires glycerol addition (recommended at 50% final concentration) and storage at -20°C/-80°C

Reconstitution Protocol:

• Briefly centrifuge the vial before opening to bring contents to the bottom

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

• Add glycerol to 5-50% final concentration for long-term storage

• Store in a Tris/PBS-based buffer containing 6% Trehalose, pH 8.0

These conditions maintain protein integrity and function while minimizing degradation through multiple use cycles .

What expression systems are most effective for producing recombinant P. atlantica atpB protein?

E. coli expression systems have proven effective for the production of recombinant P. atlantica atpB protein. The recombinant protein is typically expressed with an N-terminal His-tag to facilitate purification through affinity chromatography .

When designing expression systems for Pseudoalteromonas proteins, researchers should consider:

• Codon optimization for the expression host (especially important when expressing marine bacterial proteins in E. coli)

• Appropriate fusion tags (His-tag being commonly used)

• Induction conditions that maximize protein yield while maintaining solubility

• Purification strategies that preserve the native protein structure

For membrane proteins like atpB, additional considerations include detergent selection for solubilization and maintaining the proper folding of transmembrane domains .

How can gene silencing approaches be adapted to study atpB function in Pseudoalteromonas species?

Gene silencing approaches, particularly PTasRNA (Paired-Termini antisense RNA) technology, can be effectively adapted to study atpB function in Pseudoalteromonas species. Based on the work with P. haloplanktis, the following methodology can be applied:

• Vector Construction:

  • Design a pB40-79-PTasRNA-atpB vector through cut-and-paste procedures using appropriate restriction enzymes

  • Include antisense sequences targeting the atpB gene with paired-termini sequences upstream and downstream

• Transformation Protocol:

  • Culture bacteria in appropriate medium (such as GG 10-10) supplemented with selection antibiotics

  • Perform transformation with the PTasRNA construct

  • Select transformants on antibiotic-containing plates

  • Verify transformation through PCR or sequencing

• Gene Silencing Induction:

  • Grow transformed cultures at optimal temperature (typically 15°C for Pseudoalteromonas)

  • Monitor growth parameters to assess the impact of atpB silencing

  • Measure ATP synthesis activity to correlate with gene silencing efficiency

How does the structure of P. atlantica atpB compare to homologous proteins in other bacterial species?

The structure of P. atlantica atpB shares fundamental features with homologous proteins in other bacterial species, but also displays unique characteristics that reflect the marine adaptation of Pseudoalteromonas. Comparative analysis reveals:

These structural comparisons provide insights into both the fundamental mechanisms of ATP synthesis and the specific adaptations that allow Pseudoalteromonas to thrive in marine environments.

What methodologies are most effective for studying the membrane topology of atpB in Pseudoalteromonas?

To effectively study the membrane topology of atpB in Pseudoalteromonas, researchers should employ a combination of computational prediction, biochemical analysis, and imaging techniques:

• Computational Approaches:

  • Transmembrane domain prediction using algorithms such as TMHMM, Phobius, or MEMSAT

  • Homology modeling based on crystallized ATP synthase structures

  • Molecular dynamics simulations to predict membrane interactions

• Biochemical Methods:

  • Cysteine scanning mutagenesis coupled with accessibility assays

  • Protease protection assays to identify cytoplasmic vs. periplasmic domains

  • Cross-linking studies to identify interaction surfaces with other subunits

• Advanced Imaging:

  • Cryo-electron microscopy of purified ATP synthase complexes

  • Super-resolution imaging of tagged atpB in cellular contexts

  • Atomic force microscopy of reconstituted membrane proteins

• Functional Assays:

  • Site-directed mutagenesis of predicted key residues followed by functional testing

  • Proton translocation assays using pH-sensitive fluorescent probes

  • ATP synthesis measurements with purified complexes in liposomes

These methodologies, used in combination, can provide a comprehensive understanding of how atpB is positioned within the membrane and how this positioning relates to its function in ATP synthesis .

What is the role of atpB in the ATP synthesis mechanism of marine bacteria like Pseudoalteromonas?

In marine bacteria like Pseudoalteromonas, atpB (ATP synthase subunit a) plays a critical role in the ATP synthesis mechanism through the following functions:

• Proton Channel Formation:

  • Forms part of the proton-conducting pathway in the F₀ domain

  • Contains crucial residues that guide protons from the periplasmic space to the c-ring interface

  • Maintains the integrity of the proton path to prevent proton leakage

• c-Ring Interaction:

  • Establishes a crucial interface with the rotating c-ring

  • Provides the stationary component against which the c-ring rotates

  • Contains specific residues that interact with protonated/deprotonated residues in the c-ring

• Energy Conversion:

  • Facilitates the conversion of proton motive force into mechanical rotation

  • Ensures unidirectional rotation of the c-ring

  • Couples membrane proton translocation to the rotational motion needed for ATP synthesis

• Environmental Adaptation:

  • May contain specific adaptations that optimize function in marine conditions

  • Could contribute to energy efficiency in the nutrient-limited marine environment

  • Potentially interfaces with unique metabolic pathways in Pseudoalteromonas

This central role in energy metabolism makes atpB essential for the survival and adaptation of Pseudoalteromonas in marine ecosystems .

How does the phylogenetic diversity of Pseudoalteromonas species affect atpB conservation and function?

The phylogenetic diversity of Pseudoalteromonas species has significant implications for atpB conservation and function, reflecting both evolutionary constraints and environmental adaptations:

• Clonal Structure Impact:

  • The highly clonal structure of Pseudoalteromonas strains, with limited recombination, has led to distinct lineages with potentially specialized atpB variants

  • Linkage disequilibrium analyses show that although recombination is present, it is not frequent enough to break associations among alleles, potentially preserving functionally optimized atpB variants

• Pigmented vs. Non-pigmented Strains:

  • The division between pigmented and non-pigmented Pseudoalteromonas strains may correlate with different selective pressures on energy metabolism

  • Pigment production, which often relates to antimicrobial activity, may be associated with specific energy demands reflected in atpB adaptations

• Habitat-Specific Adaptations:

  • Marine environments with varying temperatures, pressures, and salinities may drive adaptive changes in atpB functionality

  • Strains associated with specific marine invertebrates might show host-specific adaptations in energy metabolism genes including atpB

• Functional Conservation Despite Sequence Divergence:

  • Despite sequence variations, the critical functional residues and domains of atpB remain conserved across Pseudoalteromonas species

  • Selective pressure maintains the core functionality while allowing adaptation in less critical regions of the protein

These evolutionary patterns provide valuable insights for researchers studying the adaptation of energy metabolism in marine environments and the functional constraints on essential proteins like atpB.

What methodological approaches are recommended for comparing atpB function across different Pseudoalteromonas species?

For robust comparative analysis of atpB function across different Pseudoalteromonas species, researchers should employ a multi-faceted methodological approach:

Comparative Methodology Framework:

This integrated approach allows researchers to connect sequence variations in atpB to functional differences and ecological adaptations across the Pseudoalteromonas genus, providing insights into both evolutionary processes and potential biotechnological applications .

How do genomic and plasmid elements influence atpB expression and function in Pseudoalteromonas species?

The influence of genomic and plasmid elements on atpB expression and function in Pseudoalteromonas species is complex and multifaceted:

• Chromosomal vs. Plasmid Context:

  • While the primary atpB gene is typically chromosomally encoded, plasmid elements can indirectly influence its expression and function

  • In P. haloplanktis TAC125, the presence of the pMEGA megaplasmid has been shown to affect cellular responses to oxidative stress and biofilm formation, which may indirectly impact energy metabolism through atpB function

• Regulatory Networks:

  • Plasmid-encoded regulatory elements can interact with chromosomal genes, potentially affecting atpB expression

  • The specific genes present on plasmids like pMEGA may include factors that modulate ATP synthase assembly or activity

  • Horizontal gene transfer facilitated by plasmids may introduce variations in regulatory networks affecting energy metabolism

• Genetic Engineering Implications:

  • Gene silencing approaches like PTasRNA technology developed for plasmid curing in P. haloplanktis can be adapted to study atpB function

  • Plasmid-based expression systems offer tools for functional complementation studies of atpB variants

  • The genetic toolbox developed for manipulating plasmids in Pseudoalteromonas provides methodological approaches for atpB research

• Environmental Adaptation:

  • Plasmids often carry genes that confer adaptive advantages in specific environments

  • The interplay between these adaptive elements and core energy metabolism genes like atpB may reveal important ecological strategies

Understanding these interactions is crucial for comprehensive characterization of atpB function in its native genomic context and for developing effective genetic engineering strategies in Pseudoalteromonas species.

How can recombinant P. atlantica atpB be utilized in structural biology studies of bacterial ATP synthases?

Recombinant P. atlantica atpB offers several advanced applications in structural biology studies of bacterial ATP synthases:

• Cryo-EM Structure Determination:

  • The His-tagged recombinant atpB can be used to purify intact ATP synthase complexes for cryo-electron microscopy

  • Incorporating the recombinant protein into nanodiscs or other membrane mimetics allows for structural studies in a near-native environment

  • Site-specific labeling of the recombinant protein enables precise localization within the complex architecture

• Conformational Dynamics Studies:

  • Introduction of spectroscopic probes at specific sites in the recombinant protein enables real-time monitoring of conformational changes

  • FRET (Förster Resonance Energy Transfer) pairs can be introduced to measure distances between atpB and other subunits during the catalytic cycle

  • NMR studies of isotope-labeled recombinant atpB can provide insights into dynamic aspects not captured by static structural methods

• Structural Comparison Across Species:

  • The availability of recombinant P. atlantica atpB facilitates comparative structural studies with homologs from other bacterial species

  • This allows for the identification of marine-specific structural adaptations

  • Structural comparisons can reveal insights into the evolution of ATP synthases in different ecological niches

• Structure-Function Relationship Analysis:

  • Site-directed mutagenesis of recombinant atpB, followed by functional assays, can establish precise structure-function relationships

  • Chimeric constructs combining domains from different species can identify the structural basis for functional differences

  • Co-expression with other ATP synthase subunits can reveal assembly constraints and interaction surfaces

These applications collectively advance our understanding of the fundamental mechanisms of biological energy conversion and the specific adaptations in marine bacterial systems.

What are the potential applications of P. atlantica atpB in studying ectopic ATP synthase in cancer research?

P. atlantica atpB presents unique opportunities for comparative studies that could enhance our understanding of ectopic ATP synthase (eATP synthase) in cancer research:

• Comparative Structural Analysis:

  • Structural comparison between bacterial atpB and its human mitochondrial counterpart can reveal conserved features critical for function

  • These insights can help identify potential targeting sites for cancer therapy that disrupt ectopic ATP synthase without affecting normal mitochondrial function

  • Bacterial models provide simplified systems for initial structure-based drug screening

• Trafficking Mechanism Investigations:

  • Research on how ATP synthase complexes are transported within cells can benefit from bacterial models

  • While mitochondrial ATP synthase in cancer cells uses DRP1 and KIF5B for transport to the cell surface, bacterial systems might reveal evolutionarily conserved trafficking mechanisms

  • Understanding the fundamental principles of membrane protein trafficking from bacterial studies could inform research on cancer cell adaptations

• Functional Assay Development:

  • Recombinant bacterial ATP synthase components can be used to develop robust functional assays

  • These assays can then be adapted to screen for compounds that specifically inhibit ectopic ATP synthase activity

  • The bacterial system provides a controlled experimental platform for initial validation of targeting strategies

• Evolutionary Insights:

  • Comparative studies between bacterial and human ATP synthase can reveal evolutionary adaptations

  • These evolutionary insights might help explain why and how cancer cells exploit ectopic ATP synthase

  • Ancient conserved mechanisms might be leveraged by cancer cells in novel ways

By leveraging the relative simplicity and experimental accessibility of bacterial systems, researchers can gain valuable insights that inform more complex studies on ectopic ATP synthase in cancer cells.

How can P. atlantica atpB research contribute to understanding cold adaptation mechanisms in extremophilic bacteria?

Research on P. atlantica atpB can significantly advance our understanding of cold adaptation mechanisms in extremophilic bacteria through several approaches:

• Structural Adaptations for Cold Environments:

  • Comparative analysis of atpB from P. atlantica with homologs from mesophilic bacteria can reveal cold-adaptive structural features

  • Specific amino acid substitutions in atpB may contribute to maintaining flexibility and activity at low temperatures

  • Analysis of membrane interactions may reveal adaptations that maintain proton translocation efficiency in cold conditions

• Energetic Efficiency Studies:

  • ATP synthase efficiency at different temperatures can be measured using recombinant atpB in reconstituted systems

  • The energetic cost of ATP production in cold environments may reveal specialized adaptations

  • Comparison of ATP synthesis rates and proton/ATP ratios at various temperatures can quantify cold adaptation efficiency

• Protein-Lipid Interactions:

  • Cold adaptation often involves modifications in membrane composition

  • Studies of how atpB interacts with different lipid compositions can reveal mechanisms for maintaining function in cold environments

  • Detergent solubilization studies and reconstitution in various lipid environments can provide insights into these adaptations

• Expression and Regulation Patterns:

  • Analysis of atpB expression under different temperature conditions can reveal regulatory adaptations

  • Cold shock response elements in promoter regions may indicate specialized regulation

  • Post-translational modifications specific to cold conditions might affect atpB function and stability

These research approaches can provide valuable insights not only for basic science but also for biotechnological applications seeking to develop cold-active or cold-stable biological systems .

What are common challenges in expressing and purifying recombinant P. atlantica atpB, and how can they be addressed?

Researchers working with recombinant P. atlantica atpB frequently encounter several challenges that can be addressed with specific methodological adjustments:

• Membrane Protein Solubility Issues:

  • Challenge: As a transmembrane protein, atpB often aggregates during expression

  • Solution: Optimize expression conditions with lower induction temperatures (16-20°C), use specialized E. coli strains (C41/C43), and incorporate fusion partners that enhance solubility such as MBP (maltose-binding protein)

• Proper Folding in Heterologous Systems:

  • Challenge: Incorrect folding in E. coli expression systems

  • Solution: Co-express with chaperones (GroEL/GroES), use cold-adapted expression strategies, and consider expression in alternative systems like cell-free protein synthesis for membrane proteins

• Purification Challenges:

  • Challenge: Difficulty separating atpB from host membrane proteins

  • Solution: Optimize detergent selection (test a panel including DDM, LMNG, and digitonin), implement two-step affinity purification, and consider on-column refolding protocols

• Functional Validation:

  • Challenge: Confirming that purified recombinant atpB retains native functionality

  • Solution: Develop activity assays that measure proton translocation directly, reconstitute the protein in liposomes for functional studies, and use complementation studies in bacterial mutants

• Protein Degradation:

  • Challenge: Rapid degradation during purification and storage

  • Solution: Include protease inhibitors throughout purification, maintain cold temperatures, and optimize buffer conditions with stabilizing agents such as glycerol and specific salt concentrations

By systematically addressing these challenges, researchers can improve the yield and quality of recombinant P. atlantica atpB for structural and functional studies.

How can researchers troubleshoot inconsistent results in ATP synthase activity assays using recombinant atpB?

When encountering inconsistent results in ATP synthase activity assays using recombinant atpB, researchers should consider the following troubleshooting approaches:

• Protein Quality Assessment:

  • Verify protein integrity through SDS-PAGE and Western blotting before each assay

  • Implement quality control checkpoints such as size exclusion chromatography to ensure homogeneity

  • Use dynamic light scattering to detect aggregation that might affect functional assays

• Assay Condition Optimization:

  • Systematically vary pH, temperature, ionic strength, and divalent cation concentrations

  • Consider the impact of detergent concentration on activity (excess detergent can disrupt protein-protein interactions)

  • Develop a standard operating procedure with tight control of all variables

• Reconstitution Protocol Refinement:

  • For liposome-based assays, standardize liposome preparation (size, composition, protein:lipid ratio)

  • Ensure complete incorporation of protein into liposomes (verify by flotation assays)

  • Control the orientation of incorporated protein (inside-out vs. right-side-out vesicles)

• Interaction with Other Subunits:

  • ATP synthase function requires proper assembly of multiple subunits

  • Co-expression or co-reconstitution with other essential subunits may be necessary

  • Verify complex formation through native gel electrophoresis or analytical ultracentrifugation

• Data Analysis and Controls:

  • Implement appropriate positive and negative controls for each experiment

  • Use statistical approaches to distinguish significant activity from background

  • Consider the possibility of inhibitory contaminants in protein preparations

By systematically addressing these factors, researchers can improve the reproducibility and reliability of ATP synthase activity assays using recombinant atpB.

What methodological considerations are important when studying the interaction between atpB and other ATP synthase subunits?

When investigating interactions between atpB and other ATP synthase subunits, researchers should carefully consider several methodological aspects:

• Membrane Environment Preservation:

  • The native membrane environment is critical for proper interactions between ATP synthase subunits

  • Use of nanodiscs, amphipols, or native membrane extraction techniques can maintain the lipid environment

  • Compare results across different membrane mimetics to identify potential artifacts

• Co-expression Strategies:

  • Design co-expression systems for atpB with interacting partners

  • Consider dual-plasmid systems with compatible origins of replication

  • Implement differential tagging to enable co-purification of intact complexes

• Interaction Detection Methods:

  • Employ multiple complementary techniques:

    • Co-immunoprecipitation for stable interactions

    • Crosslinking mass spectrometry to capture transient interactions

    • FRET or BRET for real-time interaction monitoring

    • Native mass spectrometry for intact complex analysis

• Functional Validation of Interactions:

  • Establish mutagenesis strategies that disrupt specific interaction interfaces

  • Correlate structural interaction data with functional outcomes

  • Develop assays that measure both binding and functional consequences of interactions

• Computational Analysis:

  • Use molecular modeling to predict interaction interfaces

  • Employ molecular dynamics simulations to study dynamic aspects of interactions

  • Analyze coevolution patterns in sequence alignments to identify interacting regions

• Quantitative Binding Parameters:

  • Determine binding affinities under various conditions

  • Assess the impact of mutations on binding kinetics

  • Characterize the thermodynamics of interactions using techniques like isothermal titration calorimetry

By integrating these methodological considerations, researchers can gain a comprehensive understanding of how atpB interacts with other ATP synthase subunits in the context of the complete functional complex.