Isolation and Characterization of Site-directed Mutants in the Highly Conserved Dicyclohexylcarbodiimide Binding Site in Subunit III of Rhodobacter sphaeroides Cytochrome c Oxidase

Abstract

Cytochrome c oxidase (COX) is the final electron acceptor in mitochondrial respiratory chain and in many bacterial species including Rhodobacter sphaeroides. Electron transfer is coupled with the pumping of protons across the membrane. Previous work has shown that reaction of beef COX with dicyclohexylcarbodiimide (DCCD) resulted in an inhibition of proton translocation by covalently binding to the conserved amino acid residue E90 located in a nonpolar region of subunit III (SIII). E90 is involved in a bonding pair with another conserved residue H212, possibly connected by a salt bridge or a hydrogen bond pair in the three dimensional structure of SIII.