Theoretical Model of the Structure and the Reaction Mechanisms of Sulfur Oxygenase Reductase in Acidithiobacillus thiooxidans

Sulfur oxygenase reductase (SOR), which is thought to be an important enzyme involved in sulfur oxidation in many microorganisms, may play a key role in sulfur oxidation in Acidithiobacillus thiooxidans. Draft genome sequence of A. thiooxidans A01 indicated the presence of sulfur oxygenase reductase gene (sor). The complementary DNA fragment was speculated to encode a putative 311-aa full-length protein SOR. Structural analysis of SOR revealed that three cysteines located in the two conserved domains, C32 at V-G-P-K-V-C32 as well as C102 and C105 at C102-X-X-C105, might form the substrate activation and binding site. It was proposed that conserved motif H87-X3-H91-X23-E115 acted as ligands might combine with iron atom to constitute a mononuclear non-heme iron center, catalyzing the oxidation reaction of substrate.