Recombinant Psychrobacter sp. ATP synthase subunit b (atpF)

What is the structural role of atpF in Psychrobacter sp. ATP synthase?

The atpF gene encodes subunit b of ATP synthase, which forms a critical component of the peripheral stalk. This stalk functions as a stator that connects the F1 catalytic domain with the F0 membrane domain. According to research on ATP synthase biogenesis, the peripheral stalk (comprised of subunits b and b') plays an essential role in maintaining the structural integrity of the complex and enabling proper rotational catalysis . In Psychrobacter, as in other bacteria, the b subunit extends from the membrane to interact with the α and δ subunits of the F1 domain, creating a stationary scaffold against which the central rotor can turn during ATP synthesis.

How does Psychrobacter sp. atpF differ from mesophilic bacterial homologs?

Psychrobacter species, being psychrotolerant organisms adapted to cold environments, show distinctive amino acid composition patterns in their proteins that contribute to cold adaptation. Analysis of cold-adapted Psychrobacter proteins reveals:

What expression systems and protocols are most effective for producing recombinant Psychrobacter sp. atpF?

Standard expression systems using vectors with ColE1-type and p15a-type replication systems, which function well in many bacteria, have proven ineffective for Psychrobacter species. Even broad-host-range vectors like pBBR1 MCS-2 fail to replicate in Psychrobacter . For successful expression of recombinant atpF, researchers should:

• Utilize Psychrobacter-specific shuttle vectors such as:

  • pPS-NR (6,250 bp) - A narrow host range Psychrobacter-E. coli shuttle vector

  • pPS-BR (6,929 bp) - A Psychrobacter-various Proteobacteria shuttle vector

• Clone the atpF gene into these vectors using the appropriate restriction sites in the multiple cloning site (MCS)

• Introduce the recombinant plasmid via triparental mating rather than transformation:

  • Culture recipient Rifᵣ-Psychrobacter strains on LB agar at 22°C for 1 day

  • Add donor and helper strains to the pre-grown recipient strain

  • Incubate for 2 days at 22°C

  • Select transconjugants on media containing rifampin and kanamycin

  • Verify plasmid presence via alkaline lysis

• Express at lower temperatures (15-20°C) to maintain proper folding of the cold-adapted protein

What purification strategy should be employed for recombinant Psychrobacter atpF protein?

For structural and functional studies of recombinant atpF, a modified purification approach based on protocols for other bacterial ATP synthase subunits should be employed:

• Expression optimization:

  • Add a 6×His-tag to the N-terminus of atpF to facilitate purification, similar to the approach used for ATP synthase β subunit in B. pseudofirmus OF4

  • Culture cells at 15-20°C to maintain proper folding of cold-adapted proteins

• Cell lysis and initial purification:

  • Use gentle lysis methods such as osmotic shock or mild detergents to avoid denaturing the protein

  • Maintain low temperature (4°C) throughout purification to preserve native structure

  • Centrifuge at high speed to remove cell debris

• Chromatography steps:

  • Perform initial IMAC (immobilized metal affinity chromatography) using Ni-NTA resin

  • Follow with anion exchange chromatography as used successfully for ATP synthase purification

  • Consider hydrophobic interaction chromatography as a final polishing step

• Quality assessment:

  • Verify purity by SDS-PAGE

  • Confirm identity via Western blot and/or mass spectrometry

  • Assess structural integrity through circular dichroism or limited proteolysis

This approach builds on successful ATP synthase purification methods while accommodating the specific requirements of cold-adapted proteins.

How can researchers investigate the interaction between atpF and other ATP synthase subunits?

To characterize the interaction between atpF and other ATP synthase components, particularly in the context of cold adaptation, researchers should employ a multi-method approach:

• In vitro reconstitution studies:

  • Purify individual subunits (atpF/b, α, β, δ) using the methods described above

  • Combine purified components under non-denaturing conditions to study self-assembly

  • Monitor assembly using analytical ultracentrifugation or size-exclusion chromatography

  • Compare assembly efficiency at different temperatures (4°C vs. 25°C)

• Protein-protein interaction analysis:

  • Use surface plasmon resonance (SPR) to quantify binding kinetics

  • Employ isothermal titration calorimetry (ITC) to determine thermodynamic parameters

  • Perform hydrogen-deuterium exchange mass spectrometry to identify interaction interfaces

• Functional studies of reconstituted complexes:

  • Assess ATPase activity of reconstituted complexes at various temperatures

  • Compare stability of complexes formed with wild-type versus mutant atpF

  • Examine the effect of specific amino acid substitutions at interaction interfaces

These methods will provide insights into how atpF contributes to the assembly and stability of the ATP synthase complex, particularly in the context of cold adaptation.

How can researchers assess the impact of atpF mutations on ATP synthase function?

To evaluate how mutations in atpF affect ATP synthase assembly and function, researchers should implement a systematic approach:

Research on ATP synthase from B. pseudofirmus demonstrated that deletion of peripheral stalk components leads to "reduced stability of the ATP synthase rotor, reduced membrane association of the F1 domain, and reduced ATPase activity" . Similar approaches would be valuable for characterizing the role of atpF in Psychrobacter.

What methodologies are appropriate for studying cold adaptation mechanisms in Psychrobacter ATP synthase?

To investigate how Psychrobacter ATP synthase functions at low temperatures, researchers should employ complementary approaches focusing on structural flexibility and enzymatic activity:

• Comparative analyses:

  • Align atpF sequences from Psychrobacter with those from mesophilic and thermophilic bacteria

  • Calculate amino acid composition focusing on cold adaptation traits (PCAT)

  • Apply statistical methods like PCA to identify patterns associated with temperature adaptation

• Structural studies:

  • Use X-ray crystallography or cryo-EM to determine the structure of Psychrobacter ATP synthase

  • Measure structural flexibility using hydrogen-deuterium exchange mass spectrometry

  • Perform molecular dynamics simulations to predict protein motion at different temperatures

• Biochemical characterization:

  • Measure ATP hydrolysis and synthesis rates at temperatures ranging from -5°C to 30°C

  • Determine thermal stability profiles using differential scanning calorimetry

  • Analyze the temperature dependence of enzyme kinetics to calculate activation energies

Studies on P. arcticus revealed that cold adaptation involves "multiple, low-cost coping strategies" including "structural modifications that increase the flexibility of at least 50% of its proteome" , which likely extends to ATP synthase components.

How does the peripheral stalk contribute to ATP synthase stability in psychrophilic bacteria?

The peripheral stalk, including the atpF-encoded b subunit, plays a crucial role in ATP synthase stability, particularly in cold-adapted organisms. To investigate this function:

• Stability assessment:

  • Compare the thermal denaturation profiles of peripheral stalk components from Psychrobacter and mesophilic bacteria

  • Assess complex stability in the presence of destabilizing agents (chaotropes, detergents)

  • Examine resistance to proteolytic degradation at different temperatures

• Interaction studies:

  • Map the interaction surfaces between peripheral stalk components and other subunits

  • Identify salt bridges, hydrogen bonds, and hydrophobic interactions that contribute to stability

  • Determine whether these interactions differ between psychrophilic and mesophilic enzymes

• Genetic approaches:

  • Create hybrid ATP synthases with peripheral stalk components from different temperature-adapted species

  • Assess the impact of these substitutions on complex stability and function

  • Use suppressor mutation analysis to identify compensatory changes that restore function

Research on ATP synthase biogenesis indicates that the peripheral stalk is essential for proper complex assembly and function , suggesting its importance in maintaining stability across temperature ranges.

What bioinformatic approaches can elucidate atpF evolution in cold-adapted bacteria?

To investigate the evolutionary history of atpF in Psychrobacter and other cold-adapted bacteria, researchers should employ these methods:

• Phylogenetic analysis:

  • Construct phylogenetic trees based on atpF sequences from diverse bacteria

  • Compare atpF phylogeny with species phylogeny to identify potential horizontal gene transfer

  • Use clustering analysis based on the neighbor-joining model as demonstrated for Psychrobacter genomes

• Sequence analysis:

  • Calculate selection pressures (dN/dS ratios) on atpF across lineages

  • Identify sites under positive selection in cold-adapted lineages

  • Map selected sites onto structural models to assess functional significance

• Comparative genomics:

  • Analyze synteny of ATP synthase operons across bacterial species

  • Examine co-evolution of atpF with other ATP synthase components

  • Consider genome-wide adaptation patterns in cold-adapted species

These approaches can reveal whether cold adaptation of atpF occurred through convergent evolution or reflects ancestral adaptation to cold environments.

What amino acid composition patterns distinguish psychrophilic atpF from mesophilic homologs?

To characterize the cold-adapted features of Psychrobacter atpF, researchers should analyze amino acid composition patterns using this methodology:

• Sequence compilation and alignment:

  • Gather atpF sequences from Psychrobacter and related genera

  • Include sequences from bacteria adapted to different temperature ranges

  • Generate multiple sequence alignments using MAFFT or similar tools

• Compositional analysis:

  • Calculate the frequency of each amino acid and compare across temperature groups

  • Pay special attention to known cold adaptation markers:

    • Glycine content (higher in psychrophiles)

    • Proline content (lower in psychrophiles)

    • Arginine:Lysine ratio (lower in psychrophiles)

    • Acidic residue content (higher in psychrophiles)

• Structural analysis:

  • Map composition differences onto structural models

  • Analyze regions with significant compositional differences

  • Assess the impact on protein flexibility and stability

Research on cold-adapted Psychrobacter proteins has shown consistent patterns of amino acid usage that likely extend to ATP synthase components .

How has the core ATP synthase operon evolved within the Psychrobacter genus?

To investigate ATP synthase operon evolution within Psychrobacter, researchers should employ these comparative genomic approaches:

• Operon structure analysis:

  • Extract and align ATP synthase operons from available Psychrobacter genomes

  • Compare gene order, intergenic spaces, and regulatory elements

  • Identify any evidence of gene duplication, loss, or horizontal transfer

• Nucleotide sequence comparison:

  • Calculate nucleotide identity across operon components

  • Use tools like Gegenees with "fragment size of 200 bp and step size of 100 bp"

  • Generate heat maps showing similarity percentages

• Core genome positioning:

  • Determine whether ATP synthase genes belong to the core genome

  • Assess whether they show similar evolutionary patterns to other core genes

  • Compare to the finding that "core genome of Psychrobacter appears unusually large (1188 homolog groups which comprised an average of 51% of the genes in each genome)"

How can recombinant Psychrobacter atpF be utilized in ATP synthase inhibitor research?

ATP synthase is a potential drug target for antimicrobial compounds. Researchers investigating inhibitors can use recombinant Psychrobacter atpF in these approaches:

• Structural studies:

  • Determine how peripheral stalk components like atpF influence inhibitor binding to the F1 domain

  • Use recombinant atpF in co-crystallization studies with known inhibitors

  • Employ hydrogen-deuterium exchange mass spectrometry to detect conformational changes induced by inhibitors

• Functional assays:

  • Assess how peripheral stalk stability affects sensitivity to inhibitors like piceatannol that "inhibited ATP synthase activity and ATP synthesis"

  • Determine whether cold adaptation influences inhibitor binding and efficacy

  • Test whether atpF-targeted compounds can enhance the effects of F1-targeted inhibitors

• Comparative studies:

  • Compare inhibitor effects on ATP synthases with peripheral stalks from psychrophilic versus mesophilic bacteria

  • Investigate whether cold adaptation confers resistance to certain inhibitors

  • Develop screening assays using chimeric ATP synthases with components from different species

This research could identify new approaches to targeting bacterial ATP synthases, particularly in cold-adapted pathogens.

What protocols can be used to investigate atpF involvement in ATP synthase assembly?

To study the role of atpF in ATP synthase assembly, particularly in the context of cold adaptation, researchers should:

• In vivo assembly studies:

  • Create fluorescently tagged atpF constructs to visualize localization during assembly

  • Develop conditional expression systems to monitor assembly kinetics

  • Use pulse-chase experiments with labeled amino acids to track assembly progression

• In vitro reconstitution:

  • Purify individual ATP synthase components, including atpF

  • Study "the self-assembly of purified F1 subunits in different environments under non-denaturing conditions"

  • Monitor binding order and assembly intermediates by native PAGE and analytical ultracentrifugation

• Mutational analysis:

  • Generate deletion and point mutations in atpF

  • Assess their impact on assembly using the methods described above

  • Identify critical residues and regions for proper assembly

Research on bacterial F-type ATP synthases has shown they "follow a well-choreographed assembly process" , and understanding atpF's role in this process could provide insights into both basic biology and potential therapeutic approaches.

How can cold-adapted features of Psychrobacter atpF inform protein engineering efforts?

The cold-adapted properties of Psychrobacter atpF offer valuable insights for protein engineering. Researchers can leverage these features through:

• Structure-guided mutagenesis:

  • Identify cold-adaptation features in Psychrobacter atpF

  • Introduce these features into mesophilic homologs through site-directed mutagenesis

  • Assess the impact on protein flexibility, stability, and function at low temperatures

• Domain swapping:

  • Create chimeric proteins with domains from psychrophilic and mesophilic atpF

  • Determine which regions contribute most significantly to cold adaptation

  • Design proteins with optimized function across temperature ranges

• Application testing:

  • Evaluate engineered proteins in biotechnological applications requiring low-temperature function

  • Test stability and activity under conditions relevant to industrial processes

  • Compare performance to both wild-type psychrophilic and mesophilic proteins

Understanding how Psychrobacter has evolved "multiple, low-cost coping strategies" for cold adaptation provides valuable lessons for engineering proteins with enhanced properties for biotechnological applications.