THE HIGHLY CONSERVED METHIONINE OF SUBUNIT-I OF THE HEME-COPPER OXIDASES IS NOT AT THE HEME-COPPER DINUCLEAR CENTER - MUTAGENESIS OF M110 IN SUBUNIT-I OF CYTOCHROME BO(3)-TYPE UBIQUINOL OXIDASE FROM ESCHERICHIA-COLI

A common feature within the heme-copper oxidase superfamily is the din uclear heme-copper center, Analysis via extended X-ray absorption fine structure (EXAFS) has led to the proposal that sulfur may be bound to Cu-B, a component of the dinuclear center, and a highly conserved met hionine (M110 in the E. coli oxidase) in subunit I has been proposed a s the ligand, Recent models of subunit I, however, suggest that this r esidue is unlikely to be near Cu-B, but is predicted to be near the lo w spin heme component of the heme-copper oxidases, In this paper, the role of M110 is examined by spectroscopic analyses of site-directed mu tants of the bo(3)-type oxidase from Escherichia coli. The results sho w that M110 is a non-essential residue and suggest that it is probably not near the heme-copper dinuclear center.