Recombinant Haemophilus somnus ATP synthase subunit a (atpB)

What is Haemophilus somnus ATP synthase subunit a (atpB)?

ATP synthase subunit a (atpB) is a critical component of the F0 sector of ATP synthase in Haemophilus somnus (now reclassified as Histophilus somni strain 129Pt). It functions as an integral membrane protein within the F-ATPase complex, facilitating proton translocation across the membrane during ATP synthesis. The protein has alternative names including ATP synthase F0 sector subunit a and F-ATPase subunit 6, with a UniProt accession number of Q0I5W7 . The full-length protein consists of 265 amino acids with a molecular structure that includes transmembrane domains critical for proton channel formation.

What is the amino acid sequence of H. somnus ATP synthase subunit a?

The complete amino acid sequence of H. somnus ATP synthase subunit a is:
MAGHTTADYISHHLTFLTTGQGFWNVHLDTLFFSLVSGVLFLFFFYRTASKATSGVPGKFQCLVEMLVEWVDGVVKDNIHGSDVRHQGSLALTIFCWVFVMNALIDLIPVDFPPQFAELLGIHYLRAVPTADISATLGMSVCVFALIFYTIKSKGLGGFVKEYTLHPFNHWAFIPVNFLEAVTLLAKPISLAFRLFGNMYAGELIFVLIAVMYMADNIIPQVLGIPLHLIWAIFHILVITLQAFIFMMLTAVYLSIAYNKSDH

What is the taxonomic relationship between Histophilus somni and Haemophilus somnus?

Haemophilus somnus has been reclassified as Histophilus somni. The organism is a gram-negative coccobacillus and an obligate inhabitant of bovine and ovine mucosal surfaces. It functions as an opportunistic pathogen responsible for respiratory disease and other systemic infections in cattle and sheep . The strain 129Pt is frequently used in research contexts and has been fully genome sequenced, allowing for detailed genetic analysis of virulence factors and metabolic pathways.

What are the optimal storage conditions for recombinant H. somnus ATP synthase subunit a?

Recombinant H. somnus ATP synthase subunit a should be stored at -20°C for regular use, and at -80°C for extended storage to maintain protein integrity. The protein is typically supplied in a Tris-based buffer containing 50% glycerol that has been optimized for stability . Repeated freeze-thaw cycles should be avoided as they can lead to protein denaturation and loss of activity. For working solutions, aliquots should be maintained at 4°C for no longer than one week to preserve protein functionality.

How should researchers verify protein integrity after purification or storage?

Protein integrity can be assessed through multiple complementary approaches:

Researchers should prioritize functional assays that specifically measure ATP synthase activity to confirm that the recombinant protein maintains native conformation and activity.

What expression systems are most effective for producing recombinant H. somnus ATP synthase subunit a?

While the search results don't specifically address expression systems for H. somnus ATP synthase subunit a, membrane proteins typically require specialized expression systems. Based on research with similar bacterial membrane proteins, the following systems may be considered:

• E. coli C41(DE3) or C43(DE3) - These strains are engineered for toxic membrane protein expression

• Cell-free expression systems - Allow for direct incorporation into lipid environments

• Insect cell expression - Provides eukaryotic processing while maintaining high yield

Expression should be optimized through systematic testing of induction conditions, including temperature (typically lowered to 16-20°C), inducer concentration, and duration of expression to maximize properly folded protein yield.

How can researchers effectively isolate membrane-associated ATP synthase components?

Isolation of membrane-associated ATP synthase components requires specialized techniques due to their hydrophobic nature:

• Start with gentle cell lysis methods using enzymatic approaches (lysozyme treatment) followed by mechanical disruption via French press or sonication

• Separate membrane fractions through differential centrifugation

• Solubilize membrane proteins using appropriate detergents (DDM, LDAO, or OG)

• Purify using affinity chromatography based on fusion tags engineered into the recombinant protein

• Verify purity through polyacrylamide gel electrophoresis and selective staining methods

For ATP synthase subunit a specifically, maintain pH and ionic strength conditions that minimize protein aggregation throughout the purification process.

How does H. somnus ATP synthase function relate to bacterial survival in host environments?

H. somnus is an opportunistic pathogen that must adapt to varying environmental conditions within host tissues. ATP synthase plays a critical role in energy metabolism that supports this adaptation. Research suggests H. somnus can form biofilms in vivo, which may represent a metabolically distinct state requiring modified ATP synthase activity . Under anaerobic conditions that might be encountered during infection, ATP synthase may function in reverse, hydrolyzing ATP to maintain membrane potential.

The relationship between energy metabolism and virulence is evidenced by increased expression of genes related to polysaccharide production and biofilm formation under conditions that favor persistence in the bovine host . ATP synthase function may be critical if the biofilm state requires specific energy dynamics for H. somnus to persist in systemic sites.

What structural features distinguish H. somnus ATP synthase subunit a from homologous proteins in other species?

H. somnus ATP synthase subunit a contains several key structural features:

• Multiple transmembrane domains that form the proton channel

• Conserved charged residues that are essential for proton translocation

• Species-specific sequence variations that may reflect adaptation to particular environmental conditions

Comparative sequence analysis reveals similarity to ATP synthase components from related bacterial species, though with distinct features that may reflect the specific metabolic requirements of H. somnus in its ecological niche. The molecular structure includes interaction surfaces for other F0 sector subunits, creating a functional proton channel complex.

How might ATP synthase function relate to H. somnus biofilm formation?

H. somnus forms biofilms both in vitro and in vivo, with a polysaccharide matrix being a key component of the biofilm . ATP synthase may play multiple roles in biofilm formation:

• Energy provision - The shift to biofilm lifestyle requires significant energy redistribution

• pH maintenance - ATP synthase activity contributes to cytoplasmic pH homeostasis, which may be critical in the microenvironment of a biofilm

• Metabolic adaptation - Genes involved in polysaccharide production are upregulated under biofilm-forming conditions , suggesting coordinated regulation with energy metabolism

Experimental evidence indicates that genes associated with polysaccharide production are upregulated when H. somnus is grown under conditions favorable to biofilm formation compared to planktonic growth . This suggests a potential metabolic shift that may involve altered ATP synthase activity or regulation.

What methods are most appropriate for studying ATP synthase activity in H. somnus?

Multiple complementary approaches can be employed to study ATP synthase activity:

For functional studies, researchers should establish appropriate bacterial growth conditions that mimic relevant physiological states. This may include growth under low oxygen tension in a bottle filled with medium and minimal headspace with slow shaking (75 rpm) to favor biofilm formation, or growth under strict anaerobic environments using systems like BD GasPak or media containing Oxyrase .

How can researchers effectively study the role of ATP synthase in H. somnus biofilm formation?

To investigate the relationship between ATP synthase and biofilm formation, researchers could employ:

• Gene expression analysis - Use real-time quantitative reverse transcription-PCR to measure atpB expression levels under biofilm-forming versus planktonic conditions

• Mutational studies - Create defined mutations in ATP synthase components and assess impacts on biofilm formation

• Metabolic profiling - Compare energy metabolism profiles between planktonic and biofilm states

• Microscopy techniques - Employ immuno-transmission electron microscopy (ITEM) to visualize ATP synthase localization within biofilm structures

Experimental protocols should include appropriate controls and standardized methods for biofilm quantification. For instance, biofilms can be grown on coverslips in suitable media to stationary phase and fixed overnight in a mixture of 4% paraformaldehyde and 5% dimethyl sulfoxide for subsequent analysis .

What are the major challenges in working with recombinant H. somnus ATP synthase subunit a?

Researchers face several challenges when working with this membrane protein:

• Protein solubility - The hydrophobic nature of membrane proteins creates challenges for expression and purification

• Functional reconstitution - Maintaining native structure and function outside the membrane environment

• Assay development - Creating reliable functional assays that accurately reflect in vivo activity

• Structural studies - Obtaining high-resolution structural information of membrane proteins

To address these challenges, researchers should consider nanodiscs or liposome reconstitution systems to maintain the protein in a membrane-like environment. Additionally, fusion partners or solubility tags may improve expression and handling characteristics.

How can researchers differentiate between F1 and F0 sector functions in ATP synthase studies?

Differentiating between the catalytic F1 and membrane-embedded F0 sectors requires specific approaches:

• Use selective inhibitors - Oligomycin specifically inhibits the F0 sector while aurovertin targets the F1 sector

• Reconstitution experiments - Purify and reconstitute individual sectors separately to assess their specific functions

• Site-directed mutagenesis - Introduce mutations in subunit-specific regions to identify functional domains

• Subunit-specific antibodies - Generate antibodies against specific subunits to track localization and interactions

When designing experiments to study atpB specifically, researchers should consider its membrane localization and potential interactions with other F0 components to develop a comprehensive understanding of its role within the ATP synthase complex.