Recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG)

What is the amino acid sequence of Prochlorococcus marinus ATP synthase subunit b' (atpG)?

The full-length Prochlorococcus marinus ATP synthase subunit b' (atpG) protein (UniProt ID: A2BT28) consists of 153 amino acids with the following sequence:
MLAFNFFGATEGGLFDINATLPLMAIQVVALTYILNSLFFKPVGNVVEKREKFVSNNIIEAKNKLSEVKKLEADLLTQLQSARTEAQRIVSEAENESDKLYKEALELANNEANASKEKARLEIESQTSAARDQLSKQADDLSELIVNRLILEK

This sequence information is essential for researchers designing experiments involving protein expression, purification, and structural studies of this subunit.

What expression systems are suitable for producing recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG)?

Escherichia coli is the preferred expression system for recombinant production of Prochlorococcus marinus ATP synthase subunit b' (atpG). Commercial preparations typically use E. coli expression systems with N-terminal His tags to facilitate purification . When designing your own expression system, consideration should be given to:

• Codon optimization for E. coli expression

• Selection of appropriate vector systems (such as pET series vectors)

• Fusion tag selection (His-tag being common for simplified purification)

• Induction conditions optimization

Similar approaches have been used successfully for other ATP synthase subunits, such as the c subunit from spinach chloroplast ATP synthase, where synthetic genes with codons optimized for E. coli expression were designed and cloned into vectors such as pMAL-c2x, pET-32a(+), and pFLAG-MAC .

How should recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) be stored for optimal stability?

For optimal stability of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG):

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

• After reconstitution, aliquot the protein to avoid repeated freeze-thaw cycles

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

• Add glycerol to a final concentration of 5-50% (typically 50%) for long-term storage

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

• Avoid repeated freeze-thaw cycles as they can compromise protein integrity

These storage conditions help maintain the structural integrity and functional properties of the protein for experimental use.

How can the purity of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) be assessed?

The purity of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) can be assessed through several complementary techniques:

• SDS-PAGE analysis: Commercial preparations typically achieve >90% purity as determined by SDS-PAGE . This technique separates proteins based on molecular weight and allows visual assessment of purity.

• Western blotting: Using antibodies specific to the protein or the attached His-tag can confirm the identity of the protein band on the gel.

• Size exclusion chromatography: This technique can be used to assess both purity and aggregation state of the protein.

• Mass spectrometry: For precise molecular weight determination and verification of the complete amino acid sequence.

• Circular dichroism spectroscopy: To confirm that the protein maintains its expected secondary structure, particularly the alpha-helical content that is characteristic of ATP synthase subunits.

For quantitative analysis, densitometry of SDS-PAGE gels can provide an estimation of percent purity.

What cloning strategies are effective for recombinant expression of ATP synthase subunits?

Based on successful approaches with similar ATP synthase subunits, the following cloning strategies are recommended:

• Gene synthesis with codon optimization: Design a synthetic gene with codons optimized for E. coli expression, similar to approaches used for other ATP synthase subunits .

• Restriction enzyme-based cloning: Add appropriate restriction sites to the synthetic gene for directional cloning. For example:

  • Using 5' NdeI and 3' XhoI sites for insertion into pET vectors

  • Using 5' blunt end and 3' XhoI for insertion into vectors like pMAL-c2x at XmnI and XhoI sites

• High-fidelity PCR amplification: Use high-fidelity polymerases like Phusion Polymerase to amplify the gene prior to insertion into expression vectors .

• Fusion protein approach: Consider expressing the protein as a fusion with tags that enhance solubility and purification, such as:

  • His-tag for IMAC purification

  • MBP (maltose-binding protein) to enhance solubility

  • Thioredoxin (via pET-32a) for disulfide bond formation and increased solubility

A typical cloning workflow would involve:

• Gene synthesis and PCR amplification

• Restriction digestion of the gene and target vector

• Ligation of the gene into the expression vector

• Transformation into a cloning strain like DH5α

• Sequence verification

• Transformation into an expression strain like BL21(DE3)

How can functional studies of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) be conducted?

Functional studies of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) require approaches that assess its role within the ATP synthase complex:

• Reconstitution experiments: Incorporate the purified recombinant protein into liposomes or nanodiscs along with other ATP synthase subunits to assess complex formation and function.

• Protein-protein interaction studies:

  • Pull-down assays using the His-tagged protein to identify binding partners

  • Surface plasmon resonance to determine binding kinetics with other subunits

  • Cross-linking studies to capture transient interactions

• Complementation studies: Similar to approaches used for the Pro1404 gene in Prochlorococcus , create recombinant strains where the native gene is replaced with modified versions to study function in vivo.

• Structural characterization:

  • Circular dichroism to confirm secondary structure

  • NMR spectroscopy for detailed structural information

  • X-ray crystallography or cryo-EM for high-resolution structural studies, particularly in complex with other ATP synthase subunits

• ATP synthesis assays: Measure ATP production in reconstituted systems containing the recombinant b' subunit to assess functional integration.

The methodological approach should be systematic, starting with confirmation of proper folding before proceeding to more complex functional studies.

What strategies can improve the yield and solubility of recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG)?

Membrane proteins like ATP synthase subunit b' can present challenges for recombinant expression. Several strategies can improve yield and solubility:

• Optimization of expression conditions:

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

  • Varying induction temperature (typically lower temperatures like 16-20°C)

  • Adjusting IPTG concentration (often 0.1-0.5 mM)

  • Testing auto-induction media formulations

• Fusion partner selection:

  • His-tag placement optimization (N-terminal vs. C-terminal)

  • MBP fusion (enhances solubility significantly for many membrane proteins)

  • SUMO tag (improves folding and can be precisely removed)

• Membrane mimetic environments for purification:

  • Detergent screening (DDM, LMNG, etc.)

  • Amphipol stabilization

  • Nanodisc incorporation

• Buffer optimization:

  • pH screening

  • Salt concentration variation

  • Addition of glycerol or other stabilizing agents

  • Inclusion of specific lipids that might be required for stability

• Refolding strategies from inclusion bodies:

  • Solubilization in urea or guanidine hydrochloride

  • Step-wise dialysis

  • On-column refolding during purification

A systematic approach combining these strategies can significantly improve the yield of functional protein for structural and biochemical studies.

How can recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) be used to study cyanobacterial energy metabolism?

Recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) can serve as a valuable tool for understanding cyanobacterial energy metabolism through several research approaches:

• Comparative structural studies: Compare the structure and function of ATP synthase from Prochlorococcus with those from other cyanobacteria to understand evolutionary adaptations to diverse environments.

• Metabolic integration: Investigate how ATP synthase activity is coordinated with other metabolic pathways in Prochlorococcus, including the recently discovered glucose uptake pathway mediated by the Pro1404 transporter .

• Environmental adaptation studies: Examine how the ATP synthase complex responds to changes in environmental conditions relevant to oceanic environments, such as varying light levels, temperature, and nutrient availability.

• Engineering approaches: Use recombinant expression systems to introduce mutations that mimic natural variants or potential adaptations, and assess their impact on ATP synthesis efficiency.

• Systems biology integration: Combine ATP synthase studies with transcriptomic and proteomic analyses to understand the regulation of energy metabolism at the cellular level.

This integrative approach can provide insights into how this globally significant marine cyanobacterium optimizes its energy metabolism in nutrient-limited oceanic environments.

What are the key considerations for studying interactions between recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) and other ATP synthase components?

When investigating interactions between recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) and other complex components, researchers should consider:

• Stoichiometric relationships:

  • The precise ratio of subunits in the native complex

  • How stoichiometry affects assembly and function

  • Methods to control subunit ratios during reconstitution experiments

• Assembly order and kinetics:

  • Sequential addition of components to monitor assembly intermediates

  • Time-resolved studies to capture transient states

  • Identification of rate-limiting steps in complex formation

• Membrane environment requirements:

  • Lipid composition effects on subunit interactions

  • Detergent selection to maintain native-like conditions

  • Reconstitution into nanodiscs or liposomes with defined lipid composition

• Protein modification considerations:

  • Impact of tags on interaction surfaces

  • Tag removal options (TEV protease cleavage, etc.)

  • Site-specific labeling for FRET or other interaction studies

• Functional validation approaches:

  • ATP synthesis/hydrolysis assays to confirm proper assembly

  • Proton translocation measurements

  • Rotational studies for mechanical coupling assessment

A comprehensive investigation would employ multiple complementary techniques, potentially including cryo-EM, native mass spectrometry, and single-molecule approaches to fully characterize these complex protein-protein interactions.

What are common challenges in expressing and purifying recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG) and how can they be addressed?

Researchers commonly encounter several challenges when working with recombinant Prochlorococcus marinus ATP synthase subunit b' (atpG), with corresponding solutions:

The purification strategy should be tailored based on the specific properties of the protein and adapted iteratively based on experimental outcomes.

How can structural and functional studies of recombinant Prochlorococcus marinus ATP synthase components contribute to our understanding of marine cyanobacterial adaptation?

Structural and functional studies of recombinant Prochlorococcus marinus ATP synthase components, including the b' (atpG) subunit, can provide significant insights into marine cyanobacterial adaptation through several research avenues:

• Efficiency adaptations:

  • Investigating unique structural features that might enhance ATP synthesis efficiency under low-nutrient conditions

  • Comparing kinetic parameters with those of ATP synthases from other organisms

  • Examining proton/ATP ratios and their environmental significance

• Environmental stress responses:

  • Studying structural stability under conditions mimicking various ocean depths (pressure, temperature)

  • Analyzing salt tolerance mechanisms relevant to marine environments

  • Investigating light-dependent regulation of ATP synthase activity

• Metabolic integration:

  • Exploring connections between ATP synthesis and unique metabolic features of Prochlorococcus, such as its recently discovered glucose uptake capability via the Pro1404 transporter

  • Understanding how ATP synthase activity coordinates with carbon fixation under varying conditions

• Ecological implications:

  • Relating ATP synthase efficiency to the global significance of Prochlorococcus in marine carbon cycling

  • Examining how ATP synthase adaptations contribute to the organism's ability to thrive in nutrient-poor oceanic regions

• Evolutionary insights:

  • Comparative analyses with ATP synthases from other cyanobacteria and photosynthetic organisms

  • Identification of unique adaptations that might represent evolutionary innovations

Such studies could help explain how Prochlorococcus has become one of the most abundant photosynthetic organisms on Earth, responsible for a significant portion of global carbon fixation, despite its apparently simplified genetic makeup and metabolic capabilities.