Recombinant Rhodobacter capsulatus ATP synthase subunit b' (atpG)

What is the gene organization of ATP synthase in Rhodobacter capsulatus and where does atpG fit in this structure?

Rhodobacter capsulatus ATP synthase has its genes organized into two separate operons – a structural arrangement found predominantly in photosynthetic prokaryotes:

• F₁ sector operon (atpHAGDC): Contains five genes coding for the extrinsic sector (δ, α, γ, β, and ε subunits, respectively)

• F₀ sector operon (atpIBEXF): Contains genes for the membrane-embedded components in the order of subunits I, a, c, b', and b

The atpG gene (also designated as atpX in the F₀ operon) encodes the b' subunit of the ATP synthase . This gene arrangement with separate F₁ and F₀ operons resembles the organization found in close relatives like Rhodospirillum rubrum and Rhodopseudomonas blastica, but differs from most non-photosynthetic bacteria where all ATP synthase genes are typically arranged in a single operon .

Why is the duplication of the b subunit (resulting in b and b' subunits) significant in Rhodobacter capsulatus?

The duplication of the b subunit gene, resulting in distinct b and b' subunits (encoded by atpF and atpG/atpX, respectively), is a unique characteristic found specifically in photosynthetic prokaryotes and plant chloroplasts . This feature is significant for several reasons:

• Evolutionary significance: This duplication represents a key evolutionary adaptation in photosynthetic organisms, suggesting specialized functional requirements in these energy-transducing systems.

• Structural adaptation: The heterodimeric peripheral stalk (b/b' combination) may provide additional structural stability or regulatory capacity compared to homodimeric structures in other bacteria.

• Functional specialization: Research indicates that the b and b' subunits have evolved distinct roles in the peripheral stalk, allowing for optimized interactions with both the F₀ and F₁ sectors.

• Bioenergetic implications: The specialized b/b' structure may contribute to the ATP synthase's ability to function efficiently under the variable energetic conditions experienced by photosynthetic organisms .

What are the most effective methods for expressing and purifying recombinant R. capsulatus ATP synthase subunit b' (atpG)?

Successful expression and purification of recombinant R. capsulatus ATP synthase subunit b' requires attention to several methodological considerations:

Expression System Selection:

• E. coli-based expression: Most successful protocols utilize E. coli strains optimized for membrane protein expression (such as C41(DE3) or C43(DE3)) .

• Expression vector considerations: Vectors incorporating N-terminal His-tags facilitate purification while minimizing interference with membrane insertion .

Optimized Expression Protocol:

• Culture growth at lower temperatures (16-25°C) after induction to improve proper folding

• Use of specialized media (e.g., Terrific Broth supplemented with glucose)

• Induction at OD₆₀₀ of 0.6-0.8 with reduced IPTG concentrations (0.1-0.5 mM)

• Extended expression periods (12-16 hours) at lower temperatures

Purification Strategy:

• Cell lysis using gentle detergents (e.g., n-Dodecyl β-D-maltoside or CHAPS)

• Initial purification via immobilized metal affinity chromatography (IMAC)

• Secondary purification using ion exchange chromatography

• Final polishing step using size exclusion chromatography

Storage Considerations:

• Addition of 50% glycerol in Tris-based buffer for extended storage

• Aliquoting and storage at -80°C to prevent freeze-thaw damage

• For working stocks, storage at 4°C for up to one week is recommended

Researchers should note that protein yield and stability are significantly influenced by detergent selection and buffer composition during the purification process.

How can researchers effectively study the interaction between ATP synthase subunit b' and other components of the ATP synthase complex?

Investigating the interactions between ATP synthase subunit b' and other components requires multiple complementary approaches:

In vitro Binding Assays:

• Pull-down assays: Using His-tagged recombinant b' subunit as bait to identify binding partners within the ATP synthase complex

• Surface plasmon resonance (SPR): For quantitative measurement of binding kinetics between b' and potential interaction partners

• Isothermal titration calorimetry (ITC): To determine thermodynamic parameters of protein-protein interactions

Structural Biology Approaches:

• Cryo-electron microscopy: Particularly useful for visualizing the intact ATP synthase complex and locating the b' subunit within the structural context

• Cross-linking mass spectrometry (XL-MS): To identify amino acid residues in close proximity between interacting subunits

• Hydrogen-deuterium exchange mass spectrometry (HDX-MS): For mapping interaction interfaces and conformational changes

Genetic and Cellular Approaches:

• Site-directed mutagenesis: Systematic mutation of potential interface residues followed by functional assays

• GTA (Gene Transfer Agent)-conjugation method: A specialized technique developed for R. capsulatus that allows introduction of mutations in essential genes followed by complementation with plasmid-borne wild-type or mutated copies

• In vivo FRET approaches: Using fluorescently tagged subunits to monitor protein-protein interactions in living cells

Data integration approaches combining structural, biochemical, and genetic data provide the most comprehensive understanding of b' subunit interactions within the ATP synthase complex.

What are the functional consequences of atpG gene disruption or knockdown in R. capsulatus, and how can these be experimentally assessed?

The functional consequences of atpG disruption in R. capsulatus are significant due to the essential nature of ATP synthase in this organism . Research approaches include:

Genetic Manipulation Strategies:

• GTA-conjugation method: This specialized technique effectively introduces genomic deletions in essential genes while providing complementation via plasmid-borne wild-type genes

• Inducible knockdown systems: Using antisense RNA or CRISPR interference (CRISPRi) with inducible promoters to achieve controlled reduction in atpG expression

• Site-directed mutagenesis: Creating point mutations that affect function without completely eliminating expression

Physiological Assessment Methods:

• Growth phenotype analysis: Monitoring growth under different conditions (photoheterotrophic, photosynthetic, aerobic, anaerobic)

• Membrane potential measurements: Using fluorescent dyes (e.g., DiOC₆) to assess changes in proton motive force

• ATP synthesis assays: Measuring ATP production rates in isolated chromatophores using luciferin/luciferase systems

Biochemical and Biophysical Analyses:

• Proton slip measurements: Assessing uncoupled proton conductance through ATP synthase using pH indicators and carotenoid electrochromism in chromatophores

• ATP hydrolysis assays: Measuring ATPase activity with colorimetric phosphate detection methods

• Complex assembly analysis: Using blue native PAGE to assess ATP synthase complex formation

Research indicates that ATP synthase is essential for R. capsulatus under all tested growth conditions, as attempts to create viable deletion mutants have been unsuccessful, with cells only surviving when complemented with a functional copy of the gene .

How does the H⁺/ATP ratio of R. capsulatus ATP synthase compare with other organisms, and what experimental approaches can verify this ratio?

The H⁺/ATP ratio is a critical bioenergetic parameter that determines the minimum proton motive force (pmf) required for ATP synthesis . For R. capsulatus ATP synthase:

Comparative H⁺/ATP Ratios:

Experimental Verification Methods:

• Thermodynamic equilibrium measurements: Determining the relationship between pmf and phosphorylation potential (ΔG') at which net ATP synthesis/hydrolysis is zero

  • This involves measuring ATP synthesis rates at different artificially imposed pmf values

  • The equilibrium pmf (pmf_eq) relates directly to the H⁺/ATP ratio

• Direct proton translocation measurements: Using pH indicators with chromatophores containing a single ATP synthase per vesicle

  • Involves excitation with flashing light and monitoring relaxation of transmembrane voltage and pH difference

  • Can distinguish between coupled and uncoupled (slip) proton movements

• c-subunit counting: Since the c-ring defines the H⁺/turn ratio according to the half-channel model, structural determination of c-subunit numbers provides insight into the H⁺/ATP ratio

• Genetic engineering approaches: Creating fusion proteins that modify the coupling ratio, followed by measurement of the minimum pmf required for ATP synthesis

Research shows that the H⁺/ATP ratio influences the lower threshold of pmf required for ATP synthesis, with higher ratios enabling ATP synthesis even at lower pmf values - critical for organisms in energy-limited environments .

What genetic engineering strategies can be employed to modify the properties of the R. capsulatus ATP synthase b' subunit for enhanced bioenergetic performance?

Engineering R. capsulatus ATP synthase subunit b' presents opportunities for bioenergetic optimization through several sophisticated approaches:

Structural Modification Strategies:

• Interface engineering: Modifying residues at the interface between b' and other subunits to alter stability or flexibility

  • Key targets include the b'/δ subunit interface and b'/membrane interaction regions

  • Site-directed mutagenesis of key hydrophobic or charged residues can modulate these interactions

• Chimeric subunit construction: Creating fusion proteins combining segments from b' subunits of different species

  • Example: Exchanging domains between R. capsulatus and chloroplast b' subunits to investigate specialized functions in photosynthetic ATP synthases

  • Systematic domain swapping can help identify regions critical for specific functional properties

• H⁺/ATP ratio modification: Engineering structural elements that influence the coupling ratio

  • Recent research demonstrates that fusion of the δΔN domain to the α subunit can effectively double the H⁺/ATP ratio, allowing ATP synthesis at lower pmf values

  • Similar approaches could target the b' subunit to modify rotational coupling properties

Expression and Regulation Strategies:

• Promoter engineering: Developing systems for controlled expression levels of atpG

  • The Pnif promoter has been successfully employed for controlled gene expression in R. capsulatus under photoheterotrophic conditions

  • This approach allows tuning of b' subunit levels relative to other ATP synthase components

• Post-translational modification sites: Introduction of regulatory phosphorylation or redox-sensitive sites

  • Could enable dynamic regulation of ATP synthase activity in response to cellular energy status

  • Would require careful structural analysis to identify suitable modification sites that don't disrupt essential functions

Experimental Validation Methods:

• GTA-conjugation method: For introducing chromosomal modifications followed by complementation

• Chromatophore-based bioenergetic assays: Using isolated subcellular vesicles for functional testing

• Whole-cell phenotypic analysis: Assessing growth and ATP production under various environmental conditions

These engineering approaches could lead to ATP synthase variants with enhanced performance under specific conditions, potentially applicable in biotechnological applications using R. capsulatus as a phototrophic platform organism .

How does proton slip occur in R. capsulatus ATP synthase, and what methodologies can quantify this phenomenon?

Proton slip represents uncoupled proton translocation through ATP synthase without concomitant ATP synthesis or hydrolysis, a phenomenon particularly relevant in bioenergetic studies of R. capsulatus:

Mechanisms and Induction of Proton Slip:

Proton slip in R. capsulatus ATP synthase:

• Occurs predominantly at low nucleotide concentrations (<1 μM)

• Is induced by continuous illumination

• Represents an uncoupling of the normally tight mechanical connection between F₀ and F₁ sectors

• May serve as a regulatory mechanism to prevent excessive pmf buildup under certain conditions

Quantification Methodologies:

• Single-enzyme-per-vesicle analysis in chromatophores:

  • R. capsulatus chromatophores (sub-bacterial vesicles) provide an ideal experimental system due to their small size containing on average less than one ATP synthase complex per vesicle

  • This allows clear distinction between vesicles containing active ATP synthase and those lacking it

• Flash-induced pmf generation and monitoring:

  • Membrane energization through excitation with flashing light

  • Photometric detection of transmembrane voltage relaxation via carotenoid absorption band-shifts (electrochromism)

  • Simultaneous monitoring of ΔpH using added pH indicators

• Data analysis procedures:

  • Kinetic analysis of proton flux rates under varying conditions

  • Differentiation between coupled and uncoupled proton movements

  • Nucleotide concentration dependence studies

The research by Feniouk et al. demonstrated that R. capsulatus ATP synthase exhibits proton slip specifically under extended illumination conditions and at low nucleotide concentrations, suggesting this phenomenon may have physiological relevance in the regulation of cellular bioenergetics under specific environmental conditions .

What are the optimal protocols for reconstituting recombinant R. capsulatus ATP synthase subunit b' into liposomes for functional studies?

Reconstitution of recombinant R. capsulatus ATP synthase subunit b' into liposomes requires careful attention to multiple parameters:

Liposome Preparation:

• Lipid composition optimization:

  • A mixture of phosphatidylcholine (70%), phosphatidic acid (20%), and cholesterol (10%) often yields stable liposomes compatible with ATP synthase components

  • For studies specifically focused on R. capsulatus, incorporating native lipids extracted from R. capsulatus membranes (10-20% of total lipid content) can improve functional incorporation

• Liposome formation methods:

  • Detergent removal technique using Bio-Beads or dialysis provides gentle incorporation

  • Sonication followed by freeze-thaw cycles can improve protein incorporation but may damage protein structure

  • Extrusion through polycarbonate filters (100-400 nm) creates uniformly sized vesicles

Protein Incorporation:

• Detergent selection:

  • n-Dodecyl β-D-maltoside (DDM) at 0.05-0.1% is generally effective

  • Concentration must be carefully controlled – sufficient to solubilize protein without destabilizing liposomes

• Protein:lipid ratio optimization:

  • For b' subunit alone: 1:100 to 1:500 (w/w)

  • For studies requiring interaction with other ATP synthase components: may require specific ratios of each component

• Incorporation confirmation methods:

  • Sucrose gradient centrifugation to separate proteoliposomes from free protein

  • Freeze-fracture electron microscopy to visualize protein incorporation

  • Fluorescence quenching assays using labeled proteins

Functional Validation:

• pmf generation in proteoliposomes:

  • Acid-base transition to establish ΔpH

  • K⁺/valinomycin to establish membrane potential

  • Combined approaches to control total pmf magnitude

• Interaction studies:

  • Co-reconstitution with other ATP synthase components

  • FRET-based assays to monitor protein-protein interactions

  • Cross-linking followed by mass spectrometry analysis

The reconstitution parameters should be systematically optimized for each specific experimental question, as conditions optimal for structural studies may differ from those best suited for functional analyses.

How can researchers establish reliable in vitro translation systems for studying R. capsulatus ATP synthase assembly?

Developing reliable in vitro translation systems for R. capsulatus ATP synthase assembly studies requires specialized approaches:

Cell-Free Expression System Development:

• Extract preparation options:

  • R. capsulatus native extract: Provides proper chaperones and assembly factors but is technically challenging to prepare

  • E. coli S30 extract supplemented with R. capsulatus chaperones: A hybrid approach that balances yield with native folding

  • Commercial systems (e.g., PURE system) supplemented with membrane fractions: Provides defined components but may lack species-specific factors

• Reaction optimization:

  • Template DNA concentration: 5-20 ng/μL for plasmid DNA

  • Magnesium concentration: Critical parameter, typically 10-14 mM

  • Energy regeneration system: ATP, GTP, creatine phosphate, and creatine kinase

  • Detergent selection: Mild detergents (digitonin, DDM) at concentrations below CMC

Multi-Protein Complex Assembly Strategies:

• Sequential translation approach:

  • Express membrane components (including b') first in the presence of liposomes or nanodiscs

  • Add peripheral components in subsequent reaction

  • Allows controlled assembly pathway analysis

• Co-expression strategies:

  • Simultaneous expression of multiple ATP synthase components

  • Requires balanced expression through template ratio optimization

  • Can capture natural assembly intermediates

Assembly Monitoring Techniques:

• Real-time assembly tracking:

  • Fluorescently labeled components to monitor interactions during translation

  • Native gel electrophoresis of samples collected at different time points

  • Mass photometry to analyze complex formation at single-molecule level

• Functional validation:

  • ATP synthesis/hydrolysis assays in reconstituted systems

  • Proton pumping assays using pH-sensitive fluorophores

  • Structural integrity assessment by negative-stain electron microscopy

This system provides a powerful platform to study how the b' subunit integrates into the ATP synthase complex and how mutations affect assembly processes, complementing in vivo approaches with precise control over assembly conditions.

What are the most effective strategies for generating site-specific antibodies against R. capsulatus ATP synthase subunit b'?

Generating high-quality, site-specific antibodies against R. capsulatus ATP synthase subunit b' requires strategic approaches to overcome challenges associated with membrane protein antigens:

Antigen Design Strategies:

• Peptide-based approach:

  • Identify highly antigenic regions using prediction algorithms (e.g., Hopp-Woods, Kyte-Doolittle)

  • Select sequences from hydrophilic, surface-exposed domains

  • Optimal R. capsulatus b' subunit regions include:

    • N-terminal region (amino acids 2-18): ANETNAVEAAAAVAGHA

    • C-terminal domain (amino acids 160-176): TATAIVTALGGKADMGA

• Recombinant domain approach:

  • Express the soluble domain of b' subunit (residues ~44-186)

  • Use fusion partners (MBP, GST, SUMO) to enhance solubility

  • Include hexahistidine tag for purification

Immunization and Selection Protocol:

• Animal selection:

  • Rabbits: For polyclonal antibodies with broader epitope recognition

  • Mice/rats: For monoclonal antibody development

  • Llamas/alpacas: For nanobody production (single-domain antibodies)

• Adjuvant selection:

  • Freund's complete/incomplete adjuvant: Traditional approach but can cause tissue damage

  • TiterMax Gold: Lower side effects while maintaining immunogenicity

  • Aluminum hydroxide with CpG oligonucleotides: For more humane protocols

• Screening methods:

  • ELISA against both the immunizing antigen and full-length protein

  • Western blotting against recombinant protein and native ATP synthase

  • Immunoprecipitation of native complexes from R. capsulatus extracts

Antibody Validation and Characterization:

• Specificity testing:

  • Cross-reactivity assessment against related bacterial ATP synthase subunits

  • Pre-absorption controls with immunizing peptides

  • Testing in atpG knockdown/mutant strains

• Application-specific validation:

  • Immunohistochemistry: Fixation-compatibility testing

  • Immunoprecipitation: Buffer optimization for membrane protein extraction

  • Super-resolution microscopy: Signal-to-noise ratio optimization

These approaches provide researchers with reliable immunological tools for studying R. capsulatus ATP synthase subunit b' localization, quantification, and interaction partners in various experimental contexts.

How does the structure and function of R. capsulatus ATP synthase subunit b' compare with homologous proteins from other photosynthetic bacteria?

The structural and functional comparison of ATP synthase subunit b' across photosynthetic bacteria reveals evolutionary patterns related to bioenergetic adaptation:

Sequence Comparison:

Structural Domain Comparison:

• Transmembrane domain:

  • R. capsulatus: Single hydrophobic segment (residues ~25-45)

  • Generally conserved hydrophobic character across species but with varied length and specific residue composition

• Peripheral stalk region:

  • Highest sequence conservation in regions interacting with F₁ sector

  • Species-specific variations in regions interacting with membrane phospholipids

  • Coiled-coil domains with organizational differences reflecting adaptation to different membrane environments

• Interface with other ATP synthase components:

  • Conservation of residues interacting with the δ subunit of F₁

  • Species-specific adaptations in regions interacting with subunit a of F₀

Functional Implications:

• The heterogeneity in b' sequences correlates with adaptations to different photosynthetic lifestyles and environmental conditions

• Conservation patterns suggest that interactions with the F₁ sector are more evolutionarily constrained than membrane-anchoring domains

• Species-specific variations may reflect adaptations to different membrane compositions and energy coupling requirements

This comparative analysis provides insights into structure-function relationships and evolutionary adaptations of the b' subunit across photosynthetic organisms, informing both basic science understanding and potential protein engineering approaches.

What insights can be gained from studying ATP synthase b' subunit in R. capsulatus for understanding the evolution of heterodimeric peripheral stalks in photosynthetic organisms?

The heterodimeric peripheral stalk (b/b') found in R. capsulatus and other photosynthetic organisms represents a significant evolutionary adaptation with important implications:

Evolutionary Context:

• Phylogenetic distribution:

  • Heterodimeric b/b' found exclusively in photosynthetic prokaryotes and chloroplasts

  • Homologous homodimeric structures (b₂) in most non-photosynthetic bacteria

  • Single, different peripheral stalk structure in mitochondrial ATP synthases

• Evolutionary timeline:

  • Divergence of b and b' likely occurred after the evolution of photosynthesis

  • Conservation of the heterodimeric structure in chloroplasts suggests it predates primary endosymbiosis (~1.5 billion years ago)

  • Specific adaptations in chloroplast b/b' occurred more recently (~300 million years ago)

Comparative Sequence Analysis:

The R. capsulatus b and b' subunits have diverged significantly despite their common evolutionary origin:

• Only ~30% sequence identity between b and b' subunits

• Conserved structural motifs but with specialized sequence adaptations

• Distinct functional constraints evidenced by different patterns of conserved residues

Mechanistic Implications:

• Functional asymmetry advantages:

  • Differential interactions with F₀ and F₁ sectors

  • Enhanced structural stability during proton translocation under variable light conditions

  • Specialized regulatory interactions not possible with homodimeric structures

• Photosynthesis-specific adaptations:

  • The heterodimeric structure may provide advantages under fluctuating energy input conditions characteristic of photosynthesis

  • May contribute to optimized ATP synthase function during transitions between light and dark conditions

  • Could enable specialized regulatory mechanisms synchronized with photosynthetic electron transport

Research Approaches:

• Ancestral sequence reconstruction:

  • Computational inference of the common ancestor of b and b'

  • Experimental characterization of reconstructed ancestral proteins

• Functional complementation studies:

  • Testing whether b can substitute for b' functions and vice versa

  • Creation of chimeric b/b' proteins to map functional specializations

• Evolutionary rate analysis:

  • Comparing substitution rates between b and b' across photosynthetic lineages

  • Identifying sites under positive or purifying selection

This evolutionary perspective provides context for understanding the specialized functions of the b' subunit in R. capsulatus and offers insights into the co-evolution of photosynthesis and ATP synthesis machinery.

How can the R. capsulatus ATP synthase system be leveraged for biotechnological applications in bioenergy production?

The R. capsulatus ATP synthase system offers several promising biotechnological applications for bioenergy production due to its unique properties:

Photobiological Hydrogen Production:

• ATP synthase modification strategies:

  • Engineering b' subunit to alter the H⁺/ATP ratio can redirect proton flux toward hydrogen production

  • Controlled expression of modified ATP synthase variants can balance cell growth with hydrogen production

• Integration with hydrogen metabolism:

  • R. capsulatus naturally contains hydrogenase enzymes

  • ATP synthase engineering can be coupled with hydrogenase overexpression

  • Potential for light-driven hydrogen production using modified ATP synthase to control energy allocation

Bioelectrochemical Systems:

• ATP synthase as a nanomotor:

  • Immobilization of engineered ATP synthase containing modified b' subunits on electrodes

  • Creation of biomolecular motors powered by artificial proton gradients

  • Potential for nanoscale energy conversion devices

• Microbial fuel cell applications:

  • Engineered R. capsulatus strains with modified ATP synthase for enhanced electron transfer to electrodes

  • Development of light-responsive biocathodes using photosynthetic capabilities

Metabolic Engineering for Bioproduct Synthesis:

• ATP-driven biosynthetic pathways:

  • R. capsulatus has been successfully engineered as a phototrophic platform for sesquiterpenoid production

  • Modified ATP synthase can be used to balance ATP supply with demands of engineered metabolic pathways

  • Engineering the b' subunit could create conditional ATP synthase activity coordinated with product synthesis pathways

• Implementation strategy:

  • Initial characterization using the Pnif promoter system already validated in R. capsulatus

  • Creation of strains with b' variants exhibiting different coupling efficiencies

  • Integration with metabolic models to predict optimal energy allocation strategies

These applications harness the unique photosynthetic and bioenergetic capabilities of R. capsulatus, with the ATP synthase b' subunit serving as a key engineering target for controlling energy conversion and allocation in biotechnological systems.

What experimental approaches can determine if the unique properties of R. capsulatus ATP synthase subunit b' contribute to the organism's adaptability to variable light conditions?

The unique properties of R. capsulatus ATP synthase subunit b' may contribute significantly to the organism's ability to adapt to fluctuating light conditions – a hypothesis that can be tested through various experimental approaches:

Physiological Characterization Under Variable Light:

• Dynamic growth experiments:

  • Compare wild-type R. capsulatus with strains expressing modified b' subunits

  • Growth under defined light regimens (constant, fluctuating, and light-dark cycles)

  • Measurement of growth rates, ATP/ADP ratios, and pmf components during light transitions

• Real-time bioenergetic measurements:

  • Carotenoid band shift measurements to track membrane potential changes during light transitions

  • Simultaneous monitoring of ΔpH using pH-sensitive fluorescent dyes

  • Assessment of ATP synthesis rates under fluctuating light using luciferase-based reporters

Molecular Adaptation Studies:

• Rapid adaptation experiments:

  • Analysis of ATP synthase complex stability during light-dark transitions

  • Assessment of proton slip induction kinetics under varying light intensities

  • Monitoring of potential post-translational modifications of b' under changing light conditions

• Protein-protein interaction dynamics:

  • FRET-based sensors to monitor b-b' interactions under different light regimens

  • Cross-linking experiments at different time points during light transitions

  • Co-immunoprecipitation studies to detect light-dependent changes in the ATP synthase interactome

Comparative Studies:

• Cross-species analysis:

  • Comparison of R. capsulatus with photosynthetic bacteria containing homodimeric b stalks

  • Heterologous expression of R. capsulatus b' in other bacteria and assessment of light adaptability

  • Creation of chimeric b' proteins combining domains from different photosynthetic organisms

• Mutant complementation approach:

  • Construction of R. capsulatus strains expressing b' variants from organisms adapted to different light environments

  • Systematic assessment of adaptation capabilities under defined light regimens

  • Correlation of functional properties with sequence/structural features