Recombinant Macrococcus caseolyticus ATP synthase subunit a (atpB)

How does Macrococcus caseolyticus atpB differ from ATP synthase components in other bacterial species?

Macrococcus caseolyticus atpB shares structural similarities with ATP synthase subunits from other bacterial species but possesses distinct sequence characteristics. Comparative genomic analyses reveal that M. caseolyticus atpB shares limited sequence homology with those found in Staphylococcus species, with which Macrococcus is phylogenetically related .

Unlike some bacterial ATP synthases that function primarily in ATP synthesis, M. caseolyticus ATP synthase may exhibit adaptations related to its ecological niche. Genomic characterization demonstrates that Macrococcus species, including M. caseolyticus, have evolved specific adaptations that may influence ATP synthase function in various environmental conditions .

What expression systems are typically used for producing recombinant M. caseolyticus atpB protein?

Recombinant M. caseolyticus atpB is typically expressed in Escherichia coli expression systems. According to product information, the full-length protein (amino acids 1-240) is expressed with an N-terminal His-tag to facilitate purification . The expression vector design includes:

• Codon optimization for E. coli expression

• N-terminal His-tag fusion for affinity purification

• Use of appropriate promoter systems (typically T7 or similar inducible promoters)

• Expression conditions optimized for membrane protein production

The resulting recombinant protein can be purified using nickel affinity chromatography and is typically provided as a lyophilized powder with greater than 90% purity as determined by SDS-PAGE .

What are the optimal storage and handling conditions for recombinant M. caseolyticus atpB?

For optimal stability and activity, recombinant M. caseolyticus atpB should be handled according to these guidelines:

To prevent protein degradation:

• Avoid repeated freeze-thaw cycles

• Add 5-50% glycerol (final concentration) when preparing aliquots

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

• Use sterile techniques when handling the protein

How can researchers effectively assess the activity of recombinant M. caseolyticus atpB in vitro?

Researchers can assess the activity of recombinant M. caseolyticus atpB using several complementary approaches:

• ATP Hydrolysis Assay: Since atpB is part of ATP synthase, ATP hydrolysis activity can be measured indirectly. This is particularly relevant for ATP synthase components like GisA that contain ATP-binding cassette domains .

• Proteoliposome Reconstitution: For functional studies, the protein can be reconstituted into proteoliposomes to assess proton translocation activity:

  • Incorporate purified atpB into liposomes

  • Use pH-sensitive fluorescent dyes to monitor proton movement

  • Measure changes in fluorescence upon addition of ATP

• Binding Studies with Other ATP Synthase Subunits: Using techniques such as:

  • Surface plasmon resonance (SPR)

  • Isothermal titration calorimetry (ITC)

  • Co-immunoprecipitation assays

• Structural Analysis: Employ circular dichroism (CD) spectroscopy to confirm proper folding of the recombinant protein, particularly important for membrane proteins with significant α-helical content .

What purification challenges are specific to M. caseolyticus atpB, and how can they be addressed?

Purification of M. caseolyticus atpB presents several challenges typical of membrane proteins:

Challenges and Solutions:

• Limited Solubility:

  • Incorporate detergents during extraction (e.g., n-dodecyl-β-D-maltoside or CHAPS)

  • Use mild solubilization conditions to maintain native structure

  • Consider surfactant screening to identify optimal solubilization conditions

• Protein Aggregation:

  • Add stabilizing agents like glycerol or trehalose to purification buffers

  • Maintain low protein concentrations during purification steps

  • Consider purification at lower temperatures (4°C)

• Maintaining Functional Conformation:

  • Use lipid-detergent mixtures to provide a native-like environment

  • Avoid harsh elution conditions during affinity chromatography

  • Consider on-column refolding techniques if necessary

• Yield Optimization:

  • Adjust induction conditions (temperature, IPTG concentration, induction time)

  • Test different E. coli expression strains (BL21(DE3), C41(DE3), C43(DE3))

  • Consider fusion partners that enhance membrane protein expression

How can researchers investigate the role of M. caseolyticus atpB in bacterial energy metabolism?

Investigating M. caseolyticus atpB's role in energy metabolism requires multiple experimental approaches:

• Gene Deletion/Complementation Studies:

  • Generate atpB deletion mutants in M. caseolyticus

  • Complement with wild-type and mutant versions of the gene

  • Assess growth phenotypes under various energy-limiting conditions

• Metabolic Flux Analysis:

  • Use isotope-labeled substrates to track metabolic pathways

  • Compare wild-type and atpB-modified strains

  • Quantify changes in ATP production and proton motive force

• Membrane Potential Measurements:

  • Employ fluorescent probes (e.g., DiSC3(5)) to measure membrane potential

  • Compare effects of atpB variants on proton gradient maintenance

  • Assess response to metabolic inhibitors and changing environmental conditions

• Proteomics Approach:

  • Identify protein-protein interactions within the ATP synthase complex

  • Map energy-related adaptations in response to atpB modifications

  • Analyze post-translational modifications that may regulate activity

What is known about inhibitors of M. caseolyticus ATP synthase, and how can they be used as research tools?

While specific inhibitors for M. caseolyticus ATP synthase have not been extensively characterized, research on ATP synthase inhibitors in related organisms provides valuable insights:

• Classes of ATP Synthase Inhibitors applicable to research:

  • α-Helical basic peptide inhibitors (e.g., IF1, melittin, Syn-A2, Syn-C)

  • Oligomycin and derivatives (target the OSCP subunit)

  • Tentoxin (uncompetitive inhibitor in some species)

  • R207910 (developed for tuberculosis treatment)

  • Bz-423 (binds to OSCP)

• Research Applications:

  • Use as tools to probe ATP synthase function in M. caseolyticus

  • Investigate species-specific differences in inhibitor sensitivity

  • Develop screening assays for novel inhibitors

  • Study structure-function relationships through inhibitor binding studies

• Experimental Design Considerations:

  • Determine IC50 values for each inhibitor class

  • Characterize inhibition mechanisms (competitive, non-competitive, etc.)

  • Identify binding sites through site-directed mutagenesis

  • Assess effects on whole-cell energy metabolism

How can researchers investigate the potential role of M. caseolyticus atpB in antimicrobial resistance mechanisms?

Investigating the role of M. caseolyticus atpB in antimicrobial resistance requires:

• Expression Analysis Under Antibiotic Stress:

  • Monitor atpB expression levels in response to different antibiotics

  • Compare expression patterns between resistant and susceptible strains

  • Correlate expression changes with metabolic adaptations

• Genetic Association Studies:

  • Analyze genomic context of atpB in relation to mobile genetic elements

  • Examine sequence variations in atpB across resistant isolates

  • Investigate horizontal gene transfer patterns, particularly in light of M. caseolyticus being identified as a reservoir for SCCmec elements

• Functional Characterization:

  • Generate atpB mutants with altered expression or activity

  • Assess changes in minimum inhibitory concentrations for various antibiotics

  • Evaluate effects on bacterial fitness and virulence

• Structural Biology Approach:

  • Determine if atpB conformation affects binding of antimicrobial compounds

  • Identify potential interaction sites for antibiotic binding

  • Study structural adaptations in resistant variants

What techniques are available for studying the membrane topology and insertion of recombinant M. caseolyticus atpB?

Studying membrane topology and insertion of M. caseolyticus atpB requires specialized techniques:

• Cysteine Scanning Mutagenesis:

  • Systematically replace residues with cysteine throughout the protein

  • Use membrane-impermeable sulfhydryl reagents to identify exposed residues

  • Map topology based on accessibility patterns

• Protease Protection Assays:

  • Express atpB in membrane vesicles

  • Treat with proteases that cannot cross membranes

  • Analyze protected fragments to determine topology

• Fluorescence-Based Approaches:

  • Create GFP fusion proteins at various positions

  • Assess fluorescence quenching in different environments

  • Use FRET techniques to measure distances between protein regions

• Cryo-Electron Microscopy:

  • Visualize the protein within membrane environments

  • Determine structural organization and interactions

  • Compare with homologous proteins from other bacterial species

How does research on bacterial ATP synthase components like M. caseolyticus atpB contribute to understanding mitochondrial diseases?

Research on bacterial ATP synthase components provides valuable insights into mitochondrial diseases through evolutionary conservation:

• Comparative Structural Biology:

  • Bacterial ATP synthase serves as a model for human mitochondrial ATP synthase

  • Structural similarities allow parallel investigation of disease-causing mutations

  • Recombinant bacterial components enable functional studies difficult to perform with mitochondrial proteins

• Disease Mechanism Investigation:

  • Several mitochondrial diseases involve ATP synthase dysfunction:

    • Neuropathy, ataxia, retinitis pigmentosa syndrome

    • Familial bilateral striatal necrosis

    • Batten's disease/neuronal ceroid lipofuscinoses

    • Alzheimer's disease (linked to ATP synthase β subunit deficiency)

• Methodological Advantages:

  • Bacterial systems allow high-yield protein production

  • Site-directed mutagenesis can mimic disease-associated variants

  • In vitro reconstitution enables isolated functional studies

• Therapeutic Development Insights:

  • Understanding inhibitor mechanisms in bacterial ATP synthase informs therapeutic approaches

  • Bacterial models can screen for compounds that modulate ATP synthase activity

  • Study of bacterial ATP synthase provides insights into sidedness of inhibitor actions

What is the potential role of M. caseolyticus atpB in bacterial pathogenesis and host interactions?

The potential role of M. caseolyticus atpB in pathogenesis and host interactions can be investigated through:

• Cell Surface Expression Analysis:

  • ATP synthase components, including α-subunit, have been detected on the surface of some bacterial cells

  • In breast cancer research, ATP synthase ecto-α-subunit has been identified as a potential therapeutic target

  • Similar expression patterns may exist in bacterial species like M. caseolyticus

• Host Immune Response Studies:

  • Surface-expressed ATP synthase components can be recognized by host immunity

  • β subunit of ATP synthase has been identified as a target protein for innate antitumor cytotoxicity

  • Similar recognition mechanisms may apply to bacterial ATP synthase components

• Virulence Association Studies:

  • Analyze correlation between atpB expression and bacterial virulence in animal models

  • Investigate atpB expression changes during host colonization

  • Examine the role of ATP synthase in adaptation to host environments

• Metabolic Adaptation to Host:

  • ATP synthase function may contribute to bacterial survival in nutrient-limited host environments

  • M. caseolyticus found in dairy and animal-associated environments may show host-specific adaptations

  • Energy metabolism adaptations could influence persistence in different host niches

What strategies can overcome poor expression yield of recombinant M. caseolyticus atpB in E. coli systems?

Poor expression yield of recombinant M. caseolyticus atpB can be addressed through multiple strategies:

• Expression System Optimization:

  Strategy	Implementation
  Strain selection	Test BL21(DE3), C41(DE3), C43(DE3), Rosetta, or SHuffle strains
  Vector design	Optimize codon usage for E. coli, consider using pET or pBAD systems
  Fusion partners	Test MBP, SUMO, or GST fusions to enhance solubility
  Induction conditions	Lower temperature (16-18°C), reduce IPTG concentration (0.1-0.5 mM), extend induction time

• Protein Solubilization Approaches:

  • Co-express with chaperones (GroEL/GroES, DnaK/DnaJ/GrpE)

  • Add membrane-mimicking components to lysis buffer

  • Test different detergents for protein extraction (DDM, LDAO, CHAPS)

  • Consider cell-free expression systems for membrane proteins

• Culture Condition Modifications:

  • Use auto-induction media

  • Test different media formulations (TB, 2XYT, minimal media)

  • Optimize aeration and culture volume

  • Add specific additives like betaine, sorbitol, or ethanol to enhance membrane protein expression

How can researchers validate the proper folding and functionality of recombinant M. caseolyticus atpB?

Validating proper folding and functionality of recombinant M. caseolyticus atpB requires multiple complementary approaches:

• Structural Analysis Methods:

  • Circular Dichroism (CD) spectroscopy to assess secondary structure content

  • Fluorescence spectroscopy to evaluate tertiary structure

  • Limited proteolysis to confirm compact folding

  • Size exclusion chromatography to detect aggregation states

• Functional Assays:

  • Proton translocation using pH-sensitive fluorescent dyes

  • ATP hydrolysis activity in reconstituted systems

  • Binding assays with other ATP synthase components

  • Inhibitor sensitivity profiling compared to native protein

• Biophysical Characterization:

  • Thermal shift assays to measure protein stability

  • Dynamic light scattering to assess homogeneity

  • Surface plasmon resonance to measure interaction kinetics with known binding partners

  • Isothermal titration calorimetry for quantitative binding measurements

What are the key considerations for designing site-directed mutagenesis experiments with M. caseolyticus atpB?

When designing site-directed mutagenesis experiments for M. caseolyticus atpB, researchers should consider:

• Target Selection Based on Structural Information:

  • Focus on conserved residues identified through sequence alignments

  • Target transmembrane regions involved in proton translocation

  • Consider residues at interfaces with other ATP synthase subunits

  • Examine sites corresponding to disease-associated mutations in homologous proteins

• Mutation Type Selection:

  • Conservative substitutions to probe specific interactions

  • Alanine scanning to identify essential residues

  • Charge reversal mutations to test electrostatic interactions

  • Cysteine substitutions for accessibility studies and crosslinking

• Experimental Controls:

  • Include wild-type protein in all experiments

  • Create both loss-of-function and gain-of-function mutations

  • Generate mutations in non-critical regions as negative controls

  • Consider introducing equivalent mutations from other species to test conservation of function

• Functional Impact Assessment:

  • Evaluate effects on ATP hydrolysis activity

  • Assess membrane integration and protein stability

  • Measure proton translocation efficiency

  • Determine impacts on interactions with other ATP synthase subunits

How does ATP synthase function differ between Macrococcus caseolyticus and related species like Staphylococcus?

Comparative analysis of ATP synthase function between M. caseolyticus and Staphylococcus species reveals:

• Evolutionary Divergence:

  • Genomic characterization shows that while M. caseolyticus is related to Staphylococcus, it has distinct genetic characteristics

  • ATP synthase components may have evolved different regulatory mechanisms reflecting adaptation to different ecological niches

  • Genus-wide genomic analysis reveals 15 genomospecies within Macrococcus, suggesting potential functional diversity in ATP synthase across the genus

• Metabolic Integration:

  • M. caseolyticus demonstrates distinctive proteolytic and lipolytic capabilities compared to Staphylococcus

  • These metabolic differences likely influence energy requirements and ATP synthase regulation

  • Cell envelope proteinase (CEP) activity levels in M. caseolyticus may correlate with ATP synthase function in nutrient acquisition and utilization

• Experimental Approaches to Compare Function:

  • Measure ATP synthesis rates under varying pH and substrate conditions

  • Compare proton-to-ATP ratios between species

  • Analyze gene expression patterns of ATP synthase components

  • Investigate regulatory mechanisms controlling ATP synthase assembly and activity

What role does ATP synthase play in M. caseolyticus adaptation to different environmental conditions?

ATP synthase plays a crucial role in M. caseolyticus adaptation to environmental conditions:

• pH Adaptation Mechanisms:

  • ATP synthase functions in maintaining intracellular pH homeostasis

  • Expression and activity may be modulated in response to environmental pH changes

  • Proton pumping activity helps maintain membrane potential under stress conditions

• Nutrient Availability Response:

  • Energy metabolism adjustments under nutrient limitation involve ATP synthase regulation

  • M. caseolyticus has been isolated from diverse environments including cheese, bovine milk, and animal skin, suggesting metabolic versatility

  • ATP synthesis efficiency may vary based on carbon source availability

• Temperature Adaptation:

  • ATP synthase structure and function may be optimized for the temperature range encountered in host environments

  • Expression levels may change in response to temperature shifts

  • Membrane fluidity changes at different temperatures affect ATP synthase activity

• Experimental Designs to Study Environmental Adaptation:

  • Gene expression analysis under various environmental stressors

  • Enzyme activity measurements across temperature and pH ranges

  • Growth phenotyping of ATP synthase mutants under various conditions

  • Comparative genomics across strains from different ecological niches