Recombinant Beijerinckia indica subsp. indica ATP synthase subunit b/b' (atpG)

How does the ATP synthase complex function in Beijerinckia indica?

The ATP synthase in Beijerinckia indica functions as a molecular motor that couples the proton electrochemical gradient to ATP synthesis. The complex consists of two major functional domains:

• F₁ domain: Located on the cytoplasmic side, containing catalytic sites for ATP synthesis

• F₀ domain: Embedded in the membrane, forming a proton channel

When protons flow through the F₀ domain down their electrochemical gradient, they induce rotational movement in the c-ring. This rotation is transmitted to the γ subunit in the F₁ domain, causing conformational changes in the β subunits where ATP synthesis occurs .

A complete 360° rotation at each catalytic site requires three conformations to be achieved and changed, with each cycle concluding with a 120° rotation. The β subunits possess three catalytic sites that cooperatively transition between distinct conformations: βE (empty), βDP (ADP-bound), and βTP (ATP-bound) .

What is the taxonomic and genomic context of Beijerinckia indica subsp. indica ATCC 9039?

Beijerinckia indica subsp. indica ATCC 9039 is classified within the following taxonomic lineage :

The genome of Beijerinckia indica subsp. indica ATCC 9039 consists of:

• Main chromosome: 4,170,153 bp

• Two plasmids: 181,736 bp and 66,727 bp

• Total of 3,982 open reading frames (ORFs)

• 3,784 protein-coding genes (2,695 with predicted functions)

• G+C content: 57.0% (56% and 54% in the plasmids)

What are the optimal conditions for reconstituting and storing recombinant B. indica ATP synthase subunit b/b'?

To ensure optimal activity of recombinant B. indica ATP synthase subunit b/b', follow these storage and reconstitution protocols:

Storage conditions:

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

• For extended storage, conserve at -20°C or -80°C

• Aliquoting is necessary for multiple use to avoid repeated freeze-thaw cycles

Reconstitution protocol:

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

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

• Add glycerol to a final concentration of 5-50% (recommended default is 50%)

• Aliquot for long-term storage at -20°C or -80°C

• For working aliquots, store at 4°C for up to one week

Important note: Repeated freezing and thawing is not recommended as it may affect protein stability and function .

How can researchers verify the purity and functionality of recombinant ATP synthase subunit b/b'?

A comprehensive approach to verifying purity and functionality involves multiple analytical techniques:

Purity assessment:

• SDS-PAGE analysis: Should show >90% purity with a single band at approximately 20 kDa

• Size exclusion chromatography: To confirm monodispersity and absence of aggregates

• Mass spectrometry: To verify the exact molecular weight and sequence integrity

Functional verification:

• Reconstitution assays: Incorporate the purified subunit into liposomes with other ATP synthase components

• ATP synthesis measurement: Establish a proton gradient across the liposome membrane and measure ATP production using a luciferase-based assay

• Binding assays: Use fluorescence anisotropy or surface plasmon resonance to verify binding to other ATP synthase subunits

• Circular dichroism: To confirm proper secondary structure formation

The purity of commercially available recombinant ATP synthase subunit b/b' is typically greater than 90% as determined by SDS-PAGE .

What experimental design approaches should be used when studying the effects of mutations in ATP synthase subunit b/b'?

When studying the effects of mutations in ATP synthase subunit b/b', a Design of Experiments (DoE) approach is recommended to systematically evaluate multiple variables. The following methodology is suggested:

Experimental design approach:

• Factor selection: Identify key factors that might influence protein function (e.g., mutations, pH, temperature, ionic strength)

• Screening design: Use fractional factorial designs to identify significant factors

• Response surface methodology: Optimize conditions around significant factors

• Center points evaluation: Include replicate center points to assess experimental variability

Implementation steps:

• Generate a comprehensive mutation library using site-directed mutagenesis

• Express and purify each mutant protein under identical conditions

• Perform functional assays under various conditions according to the DoE matrix

• Analyze data using appropriate statistical methods to identify significant effects and interactions

Analysis methods:

• Analyze model quality using p-values

• Evaluate for lack of fit

• Use confidence levels to assess reliability of results

• Check for outliers and confounding factors

How do researchers investigate the assembly process of ATP synthase in Beijerinckia indica compared to other bacterial species?

Investigating ATP synthase assembly in Beijerinckia indica requires a comparative approach with well-studied systems like yeast and mammalian mitochondria. Current knowledge suggests the following methodological approach:

Research methodology:

• Pulse-chase labeling: Track newly synthesized ATP synthase subunits using radiolabeled amino acids or fluorescent tags

• Blue native PAGE (BN-PAGE): Identify assembly intermediates by separating native protein complexes

• Immunoprecipitation with subunit-specific antibodies: Isolate assembly intermediates and identify associated proteins

• Cryo-electron microscopy: Visualize structural details of assembly intermediates

• Genetic manipulation: Create knockout/knockdown strains for putative assembly factors

Based on research with yeast and mammalian systems, ATP synthase assembly likely involves three separate modules:

• The c-ring module

• The F₁ module

• The stator arm module (including subunit b/b')

These modules converge at the end stage of assembly. The peripheral stalk, which includes subunit b/b', is critical for the stability of the c-ring/F₁ complex .

A proposed assembly pathway includes:

• Assembly of the c-ring

• Binding of F₁

• Addition of the stator arm (including subunit b/b')

• Final addition of subunits a and A6L

What are the bioinformatic approaches for analyzing evolutionary relationships of ATP synthase subunits across bacterial species?

Advanced bioinformatic analysis of ATP synthase subunits requires a multi-faceted approach:

Methodological framework:

• Sequence retrieval: Obtain ATP synthase subunit sequences from diverse bacterial species using BLAST searches and database mining

• Multiple sequence alignment: Align sequences using software like ClustalW, MUSCLE, or T-Coffee with appropriate gap penalties

• Phylogenetic analysis:

  • Maximum likelihood methods using substitution models like JTT+G4+F

  • Bayesian inference approaches

  • Assessment of node support using bootstrap or posterior probabilities

• Ancestral sequence reconstruction: Use programs like PAML (codeml) to infer ancestral states

• Convergence/divergence analysis: Identify sites under positive selection or convergent evolution

• Protein structure analysis: Map evolutionary changes onto protein structures using PyMOL or UCSF Chimera

This approach has been successfully applied to study evolutionary patterns in ATP synthase components. For example, analysis of ATP1A paralogs (sodium-potassium ATPases) revealed that convergent evolution at sites 111 and 122 decreases with sequence divergence, and that epistatic constraints on the evolution likely depend on a small number of sites .

How do researchers investigate the potential roles of ATP synthase subunits in bacterial adaptation to environmental stressors?

Investigating the roles of ATP synthase subunits in bacterial adaptation requires integrating physiological, molecular, and evolutionary approaches:

Research methodology:

• Comparative genomics: Analyze ATP synthase gene sequences across bacterial strains adapted to different environmental conditions

• Transcriptomics: Use RNA-Seq to measure changes in gene expression under various stress conditions

• Site-directed mutagenesis: Create specific mutations in conserved or variable regions of ATP synthase subunits

• Growth assays: Measure bacterial growth rates under different stress conditions (pH, temperature, salinity)

• Bioenergetic measurements: Quantify ATP production, membrane potential, and proton gradients using fluorescent probes

• Protein-protein interaction studies: Identify stress-responsive proteins that interact with ATP synthase subunits

Beijerinckia indica is an acidophilic bacterium adapted to grow in low pH environments, suggesting its ATP synthase may have specific adaptations for functioning under acidic conditions . Research on other bacteria has shown that ATP synthase regulation can be critical for adaptation to environmental changes such as light/dark transitions, anoxia, and fluctuations in nutrient supply .

For example, in plants, 14-3-3 proteins have been found to regulate ATP synthase activity in a phosphorylation-dependent manner through direct interaction with the F₁β-subunit. This regulation represents a mechanism for adaptation to environmental changes .

What are the known inhibitors of bacterial ATP synthases and how are they used in research?

Bacterial ATP synthases can be inhibited by various compounds, which are valuable tools for studying enzyme function and potential antimicrobial targets:

Major classes of ATP synthase inhibitors:

Researchers use these inhibitors to:

• Distinguish between ATP synthesis and hydrolysis activities

• Investigate the catalytic mechanism of rotational motion

• Develop potential antimicrobials targeting bacterial energy production

• Probe the structure-function relationship of ATP synthase subunits

• Study the role of ATP synthase in bacterial physiology under various conditions

The organotin compounds are particularly useful as they inhibit both ATP hydrolysis and synthesis catalyzed by the membrane-bound F₀F₁ complex but have no effect on the ATPase activity of isolated F₁, allowing researchers to distinguish between these functions .

How can researchers investigate the role of ATP synthase in bioenergetic adaptation of Beijerinckia indica?

To investigate the role of ATP synthase in bioenergetic adaptation of Beijerinckia indica, researchers should employ a multi-faceted approach:

Methodological framework:

Beijerinckia indica is a metabolically versatile bacterium capable of growth on various organic acids, sugars, and alcohols, suggesting adaptation of its bioenergetic systems including ATP synthase . It lacks phosphofructokinase and relies on the Entner-Doudoroff or pentose phosphate pathway for sugar metabolism, which may influence its ATP production strategy .

In contrast to its close relatives in the Methylocella and Methylocapsa genera, which are specialized methanotrophs, Beijerinckia indica has likely evolved different bioenergetic strategies to support its generalist lifestyle .

What methodological approaches are used to study the relationship between ATP synthase oligomerization and membrane morphology?

ATP synthase oligomerization has been linked to membrane morphology in mitochondria and bacteria. Researchers use the following approaches to study this relationship:

Advanced methodology:

• Electron cryotomography: Visualize native membrane architecture and ATP synthase distribution at near-atomic resolution

• Blue native PAGE: Separate and identify ATP synthase monomers, dimers, and higher-order oligomers

• Chemical crosslinking: Stabilize transient interactions between ATP synthase complexes

• Fluorescence microscopy with tagged subunits: Track the dynamics of ATP synthase oligomerization in vivo

• Atomic force microscopy: Measure mechanical properties of membranes with different ATP synthase oligomeric states

• Computational modeling: Simulate the effects of ATP synthase oligomerization on membrane curvature

Research has shown that ATP synthase monomers tend to aggregate into ribbons of even-numbered oligomers and dimers in vivo. This oligomerization process shapes the cristae membranes in mitochondria, potentially providing physiological benefits .

Oligomerization of ATP synthase is critical for enhancing its activity and yielding energy by establishing and preserving local proton charge and membrane potential. This is particularly important given that ATP synthase can harbor the permeability transition pore (PTP), which is involved in cell death mechanisms .

How do researchers analyze the efficiency of ATP production in bacterial ATP synthases?

Analyzing ATP production efficiency in bacterial ATP synthases requires sophisticated biophysical and biochemical techniques:

Research methodology:

• Reconstitution in liposomes: Purify and reconstitute ATP synthase into artificial membrane systems

• Establishment of proton gradients: Generate defined proton gradients using pH jumps or light-driven proton pumps

• Real-time ATP synthesis measurements: Use luciferase-based assays to quantify ATP production kinetics

• Thermodynamic analysis: Calculate the ratio of ATP formed per proton translocated (H⁺/ATP ratio)

• Single-molecule studies: Measure rotation rates and torque generation using gold nanoparticles or fluorescent probes

• Molecular electrostatic potential calculations: Analyze the electric field within ATP synthase to understand energy conversion mechanisms

Recent studies on the electric field within ATP synthase suggest that it has exceptional enzymatic efficiency. Molecular electrostatic potential calculations have revealed that alterations in the electric field support proton movement and ATP formation, demonstrating that the enzyme operates beyond its biological catalytic role .

The enzyme's newly proposed free energy terms reveal additional vital functions:

• The potential difference between proton entry and exit enhances the electrochemical gradient

• The potential spike at proton entry acts as a kinetic barrier, indicating that ATP synthase influences proton migration

These discoveries support previous estimates that ATP synthase operates with a remarkable efficiency rate of approximately 90% .

What are the approaches for expressing and purifying recombinant ATP synthase subunits from Beijerinckia indica?

Expressing and purifying recombinant ATP synthase subunits requires specialized techniques:

Expression systems comparison:

Purification protocol:

• Clone atpG gene: Insert the B. indica atpG gene into an expression vector with an appropriate tag (His-tag is commonly used)

• Transform: Introduce the vector into E. coli expression strain (BL21(DE3) or similar)

• Induce expression: Grow cells to optimal density, then induce with IPTG or auto-induction media

• Cell lysis: Disrupt cells using sonication or pressure-based methods

• Affinity chromatography: Purify using Ni-NTA for His-tagged proteins

• Size exclusion chromatography: Further purify to remove aggregates

• Analyze purity: Confirm using SDS-PAGE (should be >90% pure)

• Functional verification: Test activity in reconstituted systems

Commercial recombinant B. indica ATP synthase subunit b/b' is typically expressed in E. coli and purified to >90% purity using these methods .

How do researchers analyze gene expression patterns of ATP synthase components in Beijerinckia under different growth conditions?

Analysis of ATP synthase gene expression patterns requires multiple complementary approaches:

Methodological framework:

• RNA isolation: Extract total RNA using specialized protocols for bacteria with high exopolysaccharide production

• RNA-Seq: Perform high-throughput sequencing of the transcriptome under various conditions

• RT-qPCR: Validate expression levels of specific ATP synthase genes

• Promoter analysis: Identify regulatory elements using bioinformatic tools and reporter gene assays

• Transcriptional start site mapping: Use 5' RACE or RNA-Seq data to identify transcription initiation sites

• Regulatory network analysis: Identify transcription factors and regulatory RNAs that control ATP synthase expression

Experimental conditions to test:

• Growth on different carbon sources (mannitol, methanol, organic acids)

• Varying oxygen concentrations

• Different pH values (pH 5.5 is optimal for B. indica)

• Nitrogen-fixing versus nitrogen-sufficient conditions

• Various growth phases (log phase versus stationary)

Beijerinckia indica has been studied under various growth conditions, including methanol and glucose as carbon sources. When grown on methanol, B. indica shows specific enzymatic adaptations, suggesting regulated expression of metabolic genes including those involved in energy production .

What genetic engineering strategies can be used to study ATP synthase function in Beijerinckia indica?

Genetic engineering of Beijerinckia indica for ATP synthase studies requires specialized approaches due to the bacterium's characteristics:

Genetic modification strategies:

• Homologous recombination: Replace native ATP synthase genes with modified versions

• CRISPR-Cas9 genome editing: Introduce precise mutations in ATP synthase genes

• Transposon mutagenesis: Generate a library of random mutants to screen for ATP synthase phenotypes

• Expression of tagged subunits: Introduce fluorescent or affinity tags to track protein localization and interactions

• Inducible expression systems: Control the expression level of native or modified ATP synthase components

• Complementation studies: Introduce wild-type genes to rescue mutant phenotypes

Technical considerations for Beijerinckia indica:

• High exopolysaccharide production complicates DNA isolation and transformation

• Acidophilic nature requires adaptation of standard protocols

• Slow growth rate necessitates extended incubation periods

• Plasmids have been identified in B. indica strains that could serve as vectors for genetic manipulation

Previous genetic studies have identified plasmids in Beijerinckia indica strains, including the sequenced strain ATCC 9039 which contains two plasmids (181,736 bp and 66,727 bp). These indigenous plasmids could potentially be developed into shuttle vectors for genetic manipulation of this bacterium .

How does ATP synthase function contribute to the ecological adaptation of Beijerinckia indica in acidic soils?

ATP synthase function plays a crucial role in the ecological adaptation of Beijerinckia indica to acidic environments:

Research methodology to investigate this relationship:

• Comparative genomics: Compare ATP synthase sequences between acidophilic and neutrophilic bacteria

• pH-dependent activity assays: Measure ATP synthase activity across a range of pH values

• Membrane isolation and characterization: Analyze membrane composition and proton permeability at different pH values

• In situ gene expression analysis: Use RNA-Seq to compare ATP synthase gene expression in native soil samples versus laboratory cultures

• Metabolic flux analysis: Trace carbon and energy flow under acidic conditions using labeled substrates

Beijerinckia indica is an acidophilic bacterium that thrives in acidic soils (pH 4.5-6.0), with optimal growth at pH 5.5 . This adaptation likely involves modifications to its ATP synthase to function efficiently under these conditions.

The evolution of acid tolerance in B. indica may involve:

• Modifications to the c-ring structure to optimize the H⁺/ATP ratio

• Adaptations in the proton channel to maintain efficient proton transport at low pH

• Regulatory mechanisms to adjust ATP synthase activity in response to external pH changes

• Integration with other acid tolerance mechanisms (e.g., membrane modifications, proton pumps)

Understanding these adaptations has broader implications for understanding bacterial evolution in extreme environments and potential biotechnological applications.

What is the relationship between nitrogen fixation and ATP synthesis in Beijerinckia indica?

Nitrogen fixation is an energy-intensive process that requires significant ATP input, creating a direct link with ATP synthase function:

Methodological approaches to study this relationship:

• Comparative bioenergetics: Measure ATP production rates during nitrogen-fixing versus non-fixing conditions

• Oxygen consumption analysis: Monitor respiratory rates during different nitrogen regimes

• Gene expression correlation: Analyze co-expression patterns between nitrogenase and ATP synthase genes

• Metabolic modeling: Create in silico models of energy flux during nitrogen fixation

• Inhibitor studies: Use specific inhibitors of ATP synthase to determine effects on nitrogen fixation rates

• Genetic manipulation: Create ATP synthase variants with altered efficiency and measure impacts on nitrogen fixation

Beijerinckia indica is a free-living nitrogen-fixing bacterium that can convert atmospheric N₂ into ammonia, a process that consumes approximately 16 ATP molecules per N₂ reduced . This high energy demand creates a significant burden on cellular metabolism and requires efficient ATP production systems.

The relationship between nitrogen fixation and ATP synthesis is likely bidirectional:

• Efficient ATP synthase function is required to support the high energy demands of nitrogen fixation

• Nitrogen fixation may trigger regulatory changes in ATP synthase expression or activity to meet increased energy demands

• Both processes must be coordinated with carbon metabolism to ensure sufficient reducing equivalents for both ATP production and nitrogen reduction

Understanding this relationship has implications for agricultural applications, as Beijerinckia has been studied for its plant growth-promoting properties .

What are common issues in purifying recombinant ATP synthase subunits from Beijerinckia and how can they be resolved?

Purifying recombinant ATP synthase subunits from Beijerinckia presents several technical challenges:

Common issues and solutions:

Method optimization approach:

• Use Design of Experiments (DoE) to systematically optimize expression and purification conditions

• Test multiple affinity tags (His, GST, MBP) to identify optimal purification strategy

• Implement high-throughput screening of buffer conditions using robotic systems

• Characterize protein stability and homogeneity using dynamic light scattering and thermal shift assays

For B. indica proteins specifically, the high exopolysaccharide production by the native bacterium suggests that recombinant expression in E. coli or other hosts is preferable to purification from the native organism .

How can researchers optimize protein reconstitution methods for ATP synthase complex assembly studies?

Optimizing protein reconstitution for ATP synthase assembly studies requires careful attention to membrane environment and complex stability:

Methodological framework:

• Lipid composition optimization:

  • Screen various lipid compositions using high-throughput approaches

  • Test native lipid extracts versus synthetic lipid mixtures

  • Evaluate the impact of charged lipids on complex stability

• Protein-to-lipid ratio optimization:

  • Test different protein:lipid ratios (typically 1:50 to 1:1000 w/w)

  • Optimize using functional assays (ATP synthesis activity)

  • Verify complex formation using analytical ultracentrifugation

• Reconstitution method selection:

  • Compare detergent removal methods (dialysis, Bio-Beads, cyclodextrin)

  • Evaluate direct incorporation into preformed liposomes

  • Test microfluidic mixing approaches for uniform vesicle formation

• Buffer optimization:

  • Screen buffer components using statistical design approaches

  • Optimize pH, salt concentration, and stabilizing additives

  • Add specific lipids that might be essential for complex stability

• Quality control methods:

  • Size distribution analysis using dynamic light scattering

  • Cryo-EM to verify complex assembly

  • Proton pumping assays using pH-sensitive fluorescent dyes

  • ATP synthesis/hydrolysis activity measurements

Researchers have successfully used these approaches to study ATP synthase assembly, demonstrating that the assembly process involves multiple modules that converge at the end stage . The peripheral stalk, which includes the b/b' subunit, is particularly important for the stability of the c-ring/F₁ complex .

How do researchers interpret complex kinetic data from ATP synthase activity assays?

Interpreting complex kinetic data from ATP synthase assays requires sophisticated analytical approaches:

Methodological framework:

• Steady-state kinetics analysis:

  • Fit data to appropriate models (Michaelis-Menten, Hill, etc.)

  • Determine key parameters (Vmax, Km, Hill coefficient)

  • Compare parameters across experimental conditions

• Pre-steady-state kinetics:

  • Use stopped-flow or quenched-flow techniques

  • Identify rate-limiting steps in the catalytic cycle

  • Resolve individual steps in the rotary mechanism

• Single-molecule analysis:

  • Track rotational motion using attached probes

  • Calculate torque and work performed during rotation

  • Correlate rotation with ATP synthesis/hydrolysis events

• Data transformation approaches:

  • Use Eadie-Hofstee, Lineweaver-Burk, or Hanes-Woolf plots for linear transformation

  • Apply global fitting across multiple datasets

  • Use numerical methods for complex kinetic models

• Statistical analysis:

  • Apply appropriate statistical tests to evaluate significance

  • Use bootstrap or Monte Carlo methods to estimate parameter uncertainty

  • Compare models using AIC or BIC criteria

Researchers studying the ATP synthase rotary mechanism have determined that a complete 360° rotation results in the formation and release of three ATP molecules. Each β subunit cycles through three conformational states (βE, βDP, and βTP) during this process, with each cycle concluding with a 120° rotation .

What approaches are used to analyze the impact of environmental factors on ATP synthase expression and activity in Beijerinckia?

Analyzing environmental impacts on ATP synthase requires integrating molecular and physiological approaches:

Research methodology:

Beijerinckia indica, as an acidophilic soil bacterium, likely has specific adaptations in its ATP synthase to function optimally under acidic conditions (pH ~5.5) . Understanding how environmental factors affect ATP synthase in this organism contributes to our knowledge of bacterial adaptation to specialized ecological niches.

How can researchers accurately compare ATP synthase function across different bacterial species?

Comparing ATP synthase function across bacterial species requires standardized approaches to account for evolutionary and physiological differences:

Methodological framework:

• Sequence-structure-function analysis:

  • Compare sequence conservation in functional domains

  • Map variations onto structural models to predict functional impacts

  • Identify species-specific adaptations in key residues

• Standardized functional assays:

  • Develop consistent protocols for measuring ATP synthesis/hydrolysis

  • Account for differences in optimal pH, temperature, and ionic conditions

  • Use purified complexes reconstituted in defined lipid environments

• Heterologous expression systems:

  • Express ATP synthase genes from different species in a common host

  • Create chimeric complexes with subunits from different species

  • Test complementation of ATP synthase mutants

• Biophysical characterization:

  • Compare proton translocation efficiency (H⁺/ATP ratio)

  • Measure rotational torque and mechanical properties

  • Determine thermal and pH stability profiles

• Evolutionary context integration:

  • Correlate functional differences with phylogenetic relationships

  • Consider ecological and metabolic adaptations

  • Account for co-evolution with other cellular systems

This comparative approach has revealed both conserved features and species-specific adaptations in ATP synthases. For example, the c-ring stoichiometry can vary between species, affecting the H⁺/ATP ratio and the bioenergetic efficiency of the enzyme .