Recombinant Ochrobactrum anthropi ATP synthase subunit b 1 (atpF1)

What is the basic structure of Ochrobactrum anthropi ATP synthase subunit b 1?

Ochrobactrum anthropi ATP synthase subunit b 1 (atpF1) is a full-length protein consisting of 205 amino acids. The protein features a specific amino acid sequence: MFVSTAFAQTATESQPAPAAGEHGAADAVHTETGVANDAGHGSGVFPPFDSTHYASQILWLAITFGLFYLFMSRVVLPRIGGVIETRRDRIAQDLEQAARLKQDADNAIAAYEQELTQARTKAASIAEAAREKGKGEADAERATAEAALERKLKEAEERIAAIKAKAMNDVGNIAEETTAEIVEQLLGTKADKASVTAAVKASNA. When expressed recombinantly, it is typically fused to an N-terminal His-tag to facilitate purification and detection . The protein is part of the F-type ATPase complex, specifically the F0 sector, which is embedded in the membrane and works in conjunction with the F1 sector to catalyze ATP synthesis or hydrolysis.

How does ATP synthase function in Ochrobactrum anthropi compared to other bacteria?

ATP synthase in O. anthropi functions similarly to other bacterial F-type ATPases, utilizing a proton gradient to synthesize ATP through a rotary mechanism. The b subunit (atpF1) serves as part of the stator that connects the F0 and F1 components. In bacterial systems including O. anthropi, ATP synthase can work bidirectionally, either synthesizing ATP during oxidative phosphorylation or hydrolyzing ATP to generate a proton gradient. The inhibitory mechanisms seen in mitochondrial ATP synthases, such as IF1 inhibition, appear to function similarly in bacterial systems, where forcible rotation in the clockwise direction (ATP synthesis direction) in the presence of ADP and Pi can reactivate inhibited ATP synthase with approximately 60% probability . This suggests conservation of regulatory mechanisms across different organisms, though specific adaptations exist in O. anthropi that may be related to its environmental niche as a soil bacterium.

What are the optimal conditions for expression and purification of recombinant O. anthropi atpF1?

For optimal expression and purification of recombinant O. anthropi atpF1, the recommended approach involves expression in E. coli expression systems with an N-terminal His-tag . After expression, the protein should be purified using standard affinity chromatography protocols. The purified protein is typically stored as a lyophilized powder and should be reconstituted in deionized sterile water to a concentration of 0.1-1.0 mg/mL. For long-term storage, adding glycerol to a final concentration of 5-50% (optimally 50%) and storing at -20°C/-80°C in aliquots is recommended to prevent degradation from repeated freeze-thaw cycles . The reconstituted protein should be stored in Tris/PBS-based buffer with 6% Trehalose at pH 8.0 for optimal stability . Working aliquots can be stored at 4°C for up to one week, but repeated freezing and thawing should be avoided to maintain protein integrity.

How can single-molecule rotation assays be adapted to study O. anthropi ATP synthase function?

Single-molecule rotation assays for O. anthropi ATP synthase can be adapted from methodologies used for other F-type ATPases. Based on similar studies, magnetic tweezers can be employed to control the angular orientation of the rotor during single-molecule rotation assays . This approach allows researchers to forcibly rotate the rotor and observe the subsequent activity of the ATP synthase. The experimental setup should include:

• Immobilization of the ATP synthase complex on a surface

• Attachment of magnetic beads to the rotor subunit

• Application of a controlled magnetic field to manipulate the rotor orientation

• Real-time observation of rotation using high-resolution microscopy

This methodology can be particularly useful for studying inhibition and activation mechanisms. Experiments should be conducted in buffers containing specific substrate compositions (e.g., 100 μM ATP, 100 μM ADP, 1 mM Pi) to mimic physiological conditions . The direction of rotation (clockwise or counterclockwise) significantly impacts activation probability, with clockwise rotation in the presence of ADP and Pi showing higher activation rates from inhibited states.

How does O. anthropi atpF1 compare structurally with ATP synthase subunits from other bacterial species?

O. anthropi atpF1 (205 amino acids) shows structural similarities with ATP synthase subunits from other bacteria, particularly those in the Alphaproteobacteria class. Comparative analysis indicates that bacterial ATP synthase b subunits are generally shorter than their eukaryotic counterparts, which average around 301 ± 40 amino acids . The protein sequence of O. anthropi atpF1 contains conserved regions characteristic of F-type ATPase b subunits, including domains involved in membrane anchoring and interaction with other subunits of the ATP synthase complex.

A comparison with other bacterial b subunits reveals that those from Betaproteobacteria, such as Burkholderia vietnamiensis (214 amino acids) and Acidovorax sp. (208 amino acids), are of similar length to O. anthropi atpF1 . This suggests evolutionary conservation of this subunit's general architecture across different bacterial lineages, despite adaptations to specific environmental niches. The hydrophobic N-terminal region serves as a membrane anchor, while the hydrophilic C-terminal region interacts with the F1 sector, features likely conserved in O. anthropi atpF1 as well.

What functional differences exist between O. anthropi ATP synthase and other bacterial ATP synthases?

While maintaining the core functional mechanism of F-type ATPases, O. anthropi ATP synthase may exhibit differences related to its adaptation to soil environments. O. anthropi, as a soil bacterium phylogenetically close to Brucella , may have developed specific regulatory mechanisms for its ATP synthase to handle fluctuating environmental conditions, including changes in pH, ion concentration, and oxygen availability.

The regulatory mechanisms of O. anthropi ATP synthase likely differ from those of intracellular pathogens like Brucella, which must adapt to the host cell environment. Unlike some specialized bacteria, O. anthropi does not exhibit classic virulence factors , suggesting its ATP synthase may not be specifically adapted for pathogenicity. Instead, it likely prioritizes efficient energy production under varying soil conditions.

How can O. anthropi atpF1 be used as a model system for studying bacterial energy metabolism?

O. anthropi atpF1 offers significant advantages as a model system for studying bacterial energy metabolism due to several factors. As a soil bacterium that is phylogenetically close to Brucella but non-pathogenic under normal circumstances , it provides a safer alternative for laboratory studies. Researchers can leverage this model to investigate fundamental aspects of bacterial bioenergetics without the biosafety concerns associated with pathogenic species.

To utilize O. anthropi atpF1 as a model system, researchers should:

• Create recombinant expression systems for wild-type and mutant forms of atpF1

• Develop in vitro assays to measure ATP synthesis/hydrolysis activities under various conditions

• Establish whole-cell bioenergetic measurements to correlate ATP synthase function with cellular physiology

• Employ comparative genomics to identify unique features of O. anthropi energy metabolism

This approach can reveal insights into bacterial adaptation to environmental stress, since soil bacteria like O. anthropi must cope with varying nutrient availability, pH, and oxygen levels. The findings could be extrapolated to understand energy metabolism in related pathogenic bacteria, potentially identifying new targets for antimicrobial development.

What potential role does atpF1 play in O. anthropi's environmental adaptation?

The atpF1 gene product likely plays a crucial role in O. anthropi's adaptation to soil environments through its function in energy production. As a component of ATP synthase, atpF1 contributes to the organism's ability to efficiently generate ATP under varying conditions, which is essential for survival in heterogeneous soil environments.

O. anthropi has been identified as an opportunistic pathogen that normally cannot establish chronic infections , suggesting its ATP synthase may be optimized for environmental persistence rather than host colonization. The gene may be regulated differently in response to environmental stressors compared to dedicated pathogens, enabling rapid adaptation to changing conditions.

The structure and function of atpF1 may contribute to O. anthropi's stress response mechanisms. Similar to the role of alkyl hydroperoxide reductases (AhpC and AhpD) in oxidative stress resistance , ATP synthase function may be modulated during stress conditions to maintain energy homeostasis. Studying how atpF1 expression and function change under various stressors could provide insights into bacterial adaptation mechanisms more broadly.

What are the main challenges in studying O. anthropi ATP synthase inhibition and how can they be addressed?

Studying O. anthropi ATP synthase inhibition presents several challenges that researchers must overcome:

• Complex membrane protein isolation: ATP synthase is a membrane-embedded complex that requires careful solubilization and purification.
  Solution: Use mild detergents optimized for membrane protein extraction and implement a two-step purification strategy using the His-tag on recombinant atpF1 . Affinity chromatography followed by size exclusion chromatography can yield pure, functional protein complexes.

• Maintaining native function after purification: Membrane proteins often lose activity during purification.
  Solution: Incorporate lipids during purification and reconstitute the purified ATP synthase into liposomes or nanodiscs to maintain a lipid environment similar to the native membrane.

• Monitoring inhibition dynamics: Traditional biochemical assays provide limited information about the kinetics of inhibition.
  Solution: Implement single-molecule approaches similar to those used for other F-type ATPases, using magnetic tweezers to control rotor orientation and observe inhibition/activation events in real-time . This approach allows precise manipulation of the ATP synthase complex and detection of transient inhibited states.

• Differentiating between specific inhibition and general protein dysfunction: Distinguishing between true inhibitory mechanisms and non-specific effects can be challenging.
  Solution: Use multiple complementary approaches, including enzyme activity assays, structural studies, and single-molecule techniques. Compare results with well-characterized ATP synthases from model organisms to identify conserved and unique features of inhibition.

How can researchers effectively study the interaction between O. anthropi ATP synthase and potential inhibitory factors?

To effectively study interactions between O. anthropi ATP synthase and potential inhibitory factors, researchers should employ a multifaceted approach:

• Binding assays: Utilize surface plasmon resonance (SPR) or isothermal titration calorimetry (ITC) to quantify binding affinities between purified ATP synthase components and candidate inhibitors. These techniques provide kinetic and thermodynamic parameters of the interactions.

• Structural studies: Apply cryo-electron microscopy (cryo-EM) to visualize the ATP synthase-inhibitor complex, as has been done with other F-type ATPases and their inhibitors . This approach can reveal the binding interface and conformational changes induced by inhibitor binding.

• Functional assays: Develop ATP synthesis/hydrolysis assays to measure the impact of potential inhibitors on enzyme activity. For instance, researchers could adapt approaches used to study IF1 inhibition, which demonstrated that both directional manipulation and the presence of ATP synthesis substrates (ADP and Pi) are required for efficient reactivation of inhibited ATP synthase .

• Molecular dynamics simulations: Complement experimental data with computational modeling to predict inhibitor binding sites and simulate the effects of inhibition on ATP synthase dynamics. This approach can generate hypotheses to be tested experimentally.

• Genetic approaches: Create O. anthropi strains with mutations in atpF1 or other ATP synthase subunits to identify residues critical for inhibitor binding. This genetic strategy can validate findings from structural and biochemical studies.

The experimental conditions should be carefully controlled, with buffer compositions (particularly pH and ion concentrations) optimized to maintain ATP synthase stability while allowing inhibitor interaction. Based on studies with other systems, researchers should consider testing both ATP synthesis and hydrolysis conditions, as the directional operation of ATP synthase significantly affects inhibitor binding and dissociation .

What emerging technologies could advance our understanding of O. anthropi ATP synthase function?

Several emerging technologies hold promise for advancing our understanding of O. anthropi ATP synthase function:

• Cryo-electron tomography: This technique allows visualization of ATP synthase in its native cellular environment, providing insights into its spatial organization and interactions with other cellular components. For O. anthropi, this could reveal unique adaptations of ATP synthase to the bacterial membrane environment.

• Time-resolved structural methods: Techniques such as time-resolved cryo-EM and X-ray free-electron laser (XFEL) crystallography can capture transient conformational states during ATP synthesis/hydrolysis. These approaches could elucidate the dynamic changes in O. anthropi ATP synthase during its catalytic cycle.

• Advanced single-molecule manipulation techniques: Building upon the magnetic tweezers approach , combining force application with fluorescence resonance energy transfer (FRET) could simultaneously monitor conformational changes and mechanical movements during ATP synthase operation. This would provide unprecedented detail about the coupling between rotor movement and catalytic events.

• Nanopore-based assays: Developing nanopore systems that can measure proton translocation through the F0 sector could directly quantify the proton pumping activity of O. anthropi ATP synthase under various conditions. This would bridge the gap between structural studies and functional measurements.

• CRISPR-based screening: High-throughput CRISPR screening in O. anthropi could identify novel genes and factors that influence ATP synthase function, potentially revealing unique regulatory mechanisms in this soil bacterium.

How might research on O. anthropi ATP synthase contribute to our understanding of bacterial bioenergetics evolution?

Research on O. anthropi ATP synthase has significant potential to enhance our understanding of bacterial bioenergetics evolution:

• Phylogenetic insights: As a member of the Alphaproteobacteria and a close relative of Brucella , O. anthropi occupies an interesting evolutionary position. Comparative analysis of its ATP synthase with those from other bacterial lineages could reveal how this essential machinery has evolved across different ecological niches.

• Adaptation signatures: Identifying unique structural or functional features of O. anthropi ATP synthase could illuminate how energy-generating systems adapt to specific environmental conditions. This could help map the evolutionary trajectory of ATP synthase from free-living soil bacteria to intracellular pathogens like Brucella.

• Horizontal gene transfer assessment: Analysis of atpF1 and other ATP synthase genes in O. anthropi could reveal instances of horizontal gene transfer that have contributed to bioenergetic adaptations. This would provide insights into the role of gene exchange in bacterial energy metabolism evolution.

• Minimal functional requirements: By studying the specific properties of O. anthropi atpF1 in comparison to other bacterial subunits of similar size (such as those from Burkholderia vietnamiensis at 214 amino acids and Acidovorax sp. at 208 amino acids) , researchers can determine the minimal structural requirements for F-type ATPase function across different bacterial lineages.

• Regulatory evolution: Investigation of how O. anthropi regulates its ATP synthase in response to environmental changes could reveal evolutionary innovations in bioenergetic regulation. Comparing these regulatory mechanisms with those of related bacteria adapted to different niches would highlight convergent and divergent evolutionary pathways in bacterial energy management.