Recombinant Thermotoga petrophila ATP synthase subunit b (atpF)

What is Thermotoga petrophila and what distinguishes it from other Thermotoga species?

Thermotoga petrophila is a hyperthermophilic bacterium belonging to the genus Thermotoga, characterized by its optimal growth temperature of ≥80°C. It was isolated from the Kubiki oil reservoir in Japan and is phylogenetically related to T. naphthophila RKU-10T . T. petrophila belongs to a distinct group of Thermotoga species that thrive at higher temperatures (≥80°C), unlike other species such as T. elfii, T. thermarum, T. subterranea, T. hypogea, and T. lettingae which grow optimally at or below 70°C .

Genomic analysis reveals that T. petrophila shares a core genome of approximately 1,470 open reading frames (ORFs) with other hyperthermophilic Thermotoga species (T. maritima, T. neapolitana, and Thermotoga sp. strain RQ2), representing about 75% of their genomes . Despite this genetic similarity, T. petrophila exhibits distinctive carbohydrate utilization patterns. For example, while other Thermotoga species primarily use glucose, T. petrophila utilizes glucose to a significantly lesser extent due to the absence of a specific glucose transporter (XylE2F2K2) that is present in the other species . Instead, T. petrophila appears to acquire glucose through the XylE1F1K1 transporter, which primarily serves to transport xylose in other Thermotoga species .

How does T. petrophila ATP synthase function under extreme temperature conditions?

As a hyperthermophile, T. petrophila has evolved several adaptations that allow its ATP synthase to function optimally at temperatures that would denature proteins from mesophilic organisms:

• Structural modifications: The amino acid composition of ATP synthase subunits, including atpF, likely features increased numbers of charged residues that form stabilizing salt bridges, enhanced hydrophobic interactions in the protein core, and strategic placement of amino acids that restrict conformational flexibility at high temperatures.

• Membrane composition: The lipid environment surrounding the F0 sector of ATP synthase in T. petrophila is adapted to maintain appropriate fluidity and structural integrity at high temperatures.

• Protein-protein interactions: The interfaces between ATP synthase subunits may feature more extensive interaction networks that provide additional stability without compromising the necessary flexibility for rotational catalysis.

• Thermostable catalytic mechanisms: The catalytic sites have evolved to maintain optimal geometric configurations for ATP synthesis despite the high kinetic energy present at elevated temperatures.

These adaptations enable T. petrophila to maintain efficient energy production under extreme conditions that would be prohibitive for most organisms.

What are the optimal expression systems for producing recombinant T. petrophila atpF?

Based on current research practices with thermophilic proteins, recombinant T. petrophila atpF can be produced using several expression systems:

• E. coli expression systems: Similar to the approach used for T. maritima proteins, E. coli BL21(DE3) Rosetta 2 cells with pET-series vectors (e.g., pET30a) have proven effective for expressing thermophilic proteins . This system typically incorporates N-terminal histidine tags to facilitate purification via metal affinity chromatography.

• Baculovirus expression systems: Commercial sources produce recombinant T. petrophila ATP synthase components using baculovirus systems . This approach may provide advantages for membrane proteins or those requiring specific post-translational modifications.

When designing expression strategies, researchers should consider:

• Temperature optimization: Lower induction temperatures (15-25°C) often improve solubility of thermophilic proteins in mesophilic hosts

• Inducer concentration: Lower IPTG concentrations (0.1-0.5 mM) for pET systems

• Media selection: Rich media or specialized formulations with osmolytes that enhance protein folding

What purification challenges are specific to recombinant T. petrophila atpF and how can they be addressed?

Purifying recombinant T. petrophila atpF presents several challenges that require specific strategies:

• Membrane protein solubilization: As a membrane protein component, atpF requires careful solubilization:

  • Use mild detergents like n-dodecyl-β-D-maltoside (DDM) or lauryl maltose neopentyl glycol (LMNG)

  • Consider amphipols or nanodiscs for maintaining native-like environment

  • Test detergent screening panels to identify optimal solubilization conditions

• Maintaining thermostability during purification:

  • Include glycerol (20-50%) in purification buffers

  • Optimize salt concentrations to mimic physiological conditions

  • Consider including stabilizing additives such as arginine or trehalose

• Storage considerations:

  • Store at -20°C or -80°C for extended periods

  • Avoid repeated freeze-thaw cycles

  • Maintain working aliquots at 4°C for up to one week

• Quality control:

  • Verify structural integrity via circular dichroism or thermal shift assays

  • Assess oligomeric state using size exclusion chromatography

  • Confirm identity using mass spectrometry

The recommended storage buffer typically consists of a Tris-based buffer with 50% glycerol, optimized specifically for this protein .

How can researchers enhance the solubility of recombinant T. petrophila atpF?

Enhancing the solubility of recombinant T. petrophila atpF requires a multi-faceted approach:

• Fusion partners and tags:

  • N-terminal solubility-enhancing tags (MBP, SUMO, thioredoxin)

  • C-terminal stabilizing elements

  • Cleavable tags to remove fusion partners after purification

• Expression optimization:

  • Co-expression with chaperones (GroEL/GroES) to assist folding

  • Low-temperature induction protocols (16-20°C for 18-24 hours)

  • Auto-induction media to provide gradual protein expression

• Construct design optimization:

  • Removal or modification of hydrophobic regions

  • Rational design based on homology modeling

  • Truncation analysis to identify stable domains

When working with recombinant proteins from T. petrophila or other Thermotoga species, it's important to recognize that expression of membrane proteins often results in lower yields of soluble protein compared to cytosolic proteins. This challenge has been documented in studies of other Thermotoga proteins, where the large catalytic subunits are typically more readily expressed in soluble form than membrane-associated or regulatory subunits .

What methods are recommended for analyzing the thermostability of recombinant T. petrophila atpF?

Analyzing the thermostability of recombinant T. petrophila atpF requires techniques that can characterize protein stability under varying temperature conditions:

• Differential Scanning Calorimetry (DSC):

  • Measures heat capacity changes during protein unfolding

  • Provides thermodynamic parameters (ΔH, ΔS, Tm)

  • Enables direct comparison of stability between wild-type and mutant variants

• Circular Dichroism (CD) Spectroscopy:

  • Monitors secondary structure changes as a function of temperature

  • Allows determination of melting temperature (Tm)

  • Can be performed with minimal sample amounts

• Thermal Shift Assays (TSA):

  • Utilizes fluorescent dyes that bind to hydrophobic regions exposed during unfolding

  • High-throughput capability for screening multiple conditions

  • Generates melting curves that reflect protein stability

• Activity Assays at Varying Temperatures:

  • Functional characterization of thermal tolerance

  • Determination of temperature optima and activity retention

  • Assessment of reversibility after heat exposure

• Limited Proteolysis:

  • Reveals conformational changes at different temperatures

  • Identifies stable domains and flexible regions

  • Provides insight into unfolding pathways

When designing these experiments, researchers should consider the hyperthermophilic nature of T. petrophila (optimal growth ≥80°C) and ensure that experimental conditions can accommodate analysis at these elevated temperatures.

How does ATP synthase subunit b from T. petrophila compare structurally with homologs from other species?

While specific structural comparisons of T. petrophila ATP synthase subunit b are not detailed in the search results, a comparative analysis approach would reveal important evolutionary adaptations:

• Sequence Comparison with Related Thermotoga Species:

  • High sequence conservation would be expected among hyperthermophilic Thermotoga species

  • The core genome shared among T. petrophila, T. maritima, T. neapolitana, and Thermotoga sp. strain RQ2 includes approximately 75% of their genes

  • Genes involved in central metabolism, including ATP synthase components, are highly conserved across Thermotoga species

• Structural Adaptations for Thermostability:

  • Increased proportion of charged residues forming salt bridges

  • Higher content of hydrophobic amino acids in the protein core

  • Potential reduction in thermolabile residues (Asn, Gln, Cys)

  • More compact packing of structural elements

• Functional Domains:

  • N-terminal membrane anchor (approximately residues 1-30)

  • Central dimerization domain with characteristic heptad repeats

  • C-terminal domain interacting with the F1 sector

• Comparative Modeling Approach:

  • Homology modeling using structures from related species

  • Molecular dynamics simulations at elevated temperatures

  • Prediction of stabilizing interactions unique to thermophilic variants

This comparative approach would highlight the molecular adaptations that enable T. petrophila ATP synthase to function at extreme temperatures and could inform protein engineering strategies for enhancing thermostability in other systems.

What are the key sequence features that contribute to the function of T. petrophila atpF?

The amino acid sequence of T. petrophila ATP synthase subunit b reveals several key features that contribute to its function in the ATP synthase complex:

These sequence features collectively enable T. petrophila atpF to perform its structural role in maintaining the peripheral stalk of ATP synthase while withstanding the extreme temperatures of its native environment.

How can recombinant T. petrophila atpF be used to study the bioenergetics of extremophiles?

Recombinant T. petrophila atpF provides a valuable tool for studying bioenergetic mechanisms in extremophiles:

• ATP Synthase Assembly Studies:

  • Investigation of assembly pathways under extreme conditions

  • Identification of chaperones or assembly factors specific to thermophiles

  • Comparison with mesophilic homologs to understand adaptation mechanisms

• Membrane Reconstitution Experiments:

  • Incorporation of purified components into liposomes

  • Measurement of proton translocation or ATP synthesis

  • Assessment of function under varying temperature and pH conditions

• Protein-Protein Interaction Analysis:

  • Characterization of interactions with other ATP synthase subunits

  • Investigation of complex stability at elevated temperatures

  • Identification of thermophile-specific interaction networks

• Connection to Hydrogen Production:

  • Thermotoga species produce hydrogen at high yields (3-4 mol/mol glucose)

  • The bioenergetics of ATP synthesis may be linked to hydrogen production via redox balance

  • Understanding energy conservation mechanisms could inform biohydrogen production strategies

• Cross-Species Complementation:

  • Expression in mesophilic hosts lacking functional ATP synthase

  • Assessment of functional complementation at different temperatures

  • Identification of compatibility factors between thermophilic and mesophilic components

These approaches would contribute to our understanding of how extremophiles maintain efficient energy coupling under conditions that would denature proteins from mesophilic organisms.

What methods are most effective for assessing the functional integration of recombinant T. petrophila atpF into ATP synthase complexes?

Assessing the functional integration of recombinant T. petrophila atpF into ATP synthase complexes requires specialized techniques:

• Subunit Assembly Assays:

  • Co-expression with other ATP synthase subunits

  • Co-immunoprecipitation to detect complex formation

  • Blue native PAGE to visualize intact complexes

  • Chemical crosslinking followed by mass spectrometry to map interaction sites

• Functional Reconstitution:

  • Integration into proteoliposomes containing other ATP synthase components

  • Measurement of ATP synthesis driven by artificially imposed proton gradients

  • Assessment of proton translocation using pH-sensitive fluorescent dyes

  • Comparative analysis with reconstituted wild-type complexes

• Structural Verification:

  • Cryo-electron microscopy of reconstituted complexes

  • Negative stain electron microscopy for initial visualization

  • Mass photometry to determine complex stoichiometry

  • Hydrogen-deuterium exchange mass spectrometry to assess structural dynamics

• Genetic Complementation:

  • Expression in ATP synthase-deficient bacterial strains

  • Measurement of growth restoration under various conditions

  • Analysis of ATP production in complemented strains

• Biophysical Characterization:

  • Fluorescence resonance energy transfer (FRET) between labeled subunits

  • Atomic force microscopy of membrane-reconstituted complexes

  • Single-molecule analysis of rotational dynamics

These methods would provide comprehensive insights into both the structural incorporation and functional contribution of recombinant T. petrophila atpF to ATP synthase activity.

How can molecular dynamics simulations enhance our understanding of T. petrophila atpF thermostability?

Molecular dynamics (MD) simulations offer powerful computational approaches to understand the thermostability mechanisms of T. petrophila atpF:

• Temperature-Dependent Simulations:

  • Parallel simulations at different temperatures (25°C, 80°C, 100°C)

  • Analysis of protein flexibility and conformational changes

  • Identification of regions that maintain rigidity at elevated temperatures

  • Comparison with mesophilic homologs at the same temperatures

• Salt Bridge and Hydrogen Bond Analysis:

  • Quantification of electrostatic interaction networks

  • Measurement of salt bridge persistence at high temperatures

  • Comparison of hydrogen bond dynamics between thermophilic and mesophilic proteins

  • Identification of critical stabilizing interactions

• Water and Ion Interactions:

  • Analysis of hydration patterns around the protein

  • Characterization of ion-binding sites that may enhance stability

  • Examination of water penetration into the protein core

  • Solvation free energy calculations at different temperatures

• Unfolding Pathway Elucidation:

  • Simulated thermal denaturation studies

  • Identification of initial unfolding regions

  • Determination of the rate-limiting steps in thermal denaturation

  • Energy barrier calculations for unfolding transitions

• In silico Mutagenesis:

  • Computational predictions of stability changes upon mutation

  • Design of potentially stabilizing mutations

  • Identification of key residues responsible for thermostability

  • Validation through experimental testing of selected mutants

Such computational approaches would provide atomic-level insights into the structural basis of thermostability that could inform protein engineering efforts and enhance our fundamental understanding of protein adaptation to extreme environments.

How do the structural and functional properties of ATP synthase differ among Thermotoga species?

Comparative analysis of ATP synthase across Thermotoga species reveals both conservation and species-specific adaptations:

• Genomic Context:

  • ATP synthase genes are part of the core genome shared among the four hyperthermophilic Thermotoga species (T. maritima, T. neapolitana, T. petrophila, and Thermotoga sp. strain RQ2)

  • Genes involved in central metabolism, including energy production, are highly conserved

• Temperature Adaptations:

  • Higher temperature Thermotoga species (T. maritima, T. petrophila, T. neapolitana, and T. naphthophila) grow optimally at ≥80°C

  • Lower temperature species (T. elfii, T. thermarum, T. subterranea, T. hypogea, and T. lettingae) grow optimally at or below 70°C

  • These temperature preferences may correlate with subtle adaptations in ATP synthase structure

• Metabolic Context:

  • All Thermotoga species produce hydrogen as a fermentation product, with yields approaching the theoretical maximum of 4 mol H2/mol glucose

  • The "bifurcating" hydrogenase in Thermotoga maritima uses both NADH and reduced ferredoxin as electron donors, allowing for efficient hydrogen production

  • This energy metabolism strategy may influence the regulation and operation of ATP synthase across species

• Species-Specific Features:

  • T. petrophila has unique adaptations for glucose utilization compared to other Thermotoga species

  • These metabolic differences may result in varying ATP demands and thus influence ATP synthase expression or regulation

While the search results don't provide specific structural comparisons of ATP synthase components between species, the high conservation of central metabolic pathways suggests that ATP synthase structure and function are likely similar across Thermotoga species, with subtle adaptations to their specific ecological niches.

What evolutionary insights can be gained from studying T. petrophila atpF in relation to other bacterial ATP synthases?

Studying T. petrophila atpF in an evolutionary context provides valuable insights into bacterial adaptation to extreme environments:

• Phylogenetic Analysis:

  • The Thermotoga genus represents a deeply branching bacterial lineage

  • Analysis of atpF sequences across this genus can illuminate early evolutionary adaptations in bacterial ATP synthases

  • Comparison with other thermophilic and mesophilic bacteria can reveal convergent evolution strategies

• Thermostability Adaptations:

  • Identification of amino acid substitutions that correlate with growth temperature

  • Analysis of structural features that emerged independently in different thermophilic lineages

  • Understanding of the minimum changes required for adaptation to high temperatures

• Horizontal Gene Transfer Assessment:

  • Evaluation of potential horizontal gene transfer events involving ATP synthase components

  • T. petrophila strain TFO, isolated from a Californian offshore oil reservoir, is phylogenetically related to T. petrophila RKU-1 and T. naphthophila RKU-10, suggesting global distribution of these species

  • Analysis of genomic islands near ATP synthase genes

• Evolutionary Rate Analysis:

  • Comparison of evolutionary rates between different ATP synthase subunits

  • Identification of conserved vs. variable regions within atpF

  • Correlation between evolutionary conservation and functional importance

• Ecological Adaptation Signatures:

  • T. petrophila and related species from oil reservoirs may show adaptations specific to these environments

  • Comparison of strains from different geographic locations could reveal local adaptations

  • Analysis of strain TFO revealed strain-specific proteins linked to glycosyltransferases and mobile genetic elements, indicating mechanisms for adaptation to environmental changes

These evolutionary perspectives can enhance our understanding of how essential cellular machinery adapts to extreme conditions while maintaining fundamental functionality.