Structural analyses of the interactions of SoxY and SoxZ from thermo-neutrophilic Hydrogenobacter thermophilus

Microbial redox reactions of inorganic sulfur compounds are one of the important reactions responsible for the recycling of this element to maintain the environmental sulfur balance. These reactions are carried out by phylogenetically diverse set of microorganisms. The sulfur oxidizing gene cluster (sox) of thermo-neutrophilic bacterium Hydrogenobacter thermophilus consists of soxYZAXB. The bacterium shows optimal thiosulfate oxidation activity at 60°C. There are practically no reports regarding the structural biology of the sulfur oxidation proc- ess in this organism. In the present context, we employed homology modeling to construct the three dimensional structures of SoxY and SoxZ from Hydrogenobacter thermophilus. With the help of docking simulations we have identified the amino acid residues of these proteins in- volved in the interactions. The thermodynamics of the protein-protein interactions have also been analyzed. The probable biochemical mechanism of the binding of thiosulfate has been elucidated. Our study provides a rational framework to understand the molecular mechanism of the sulfur oxidation biochemistry.