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EPR studies of wild‐type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides : Glu 286 is not a bridging ligand in the cytochrome a 3 ‐Cu B center
Author(s) -
D M Mitchell,
R Aasa,
P Adelroth,
P Brzezinski,
R B Gennis,
B G Malmström
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01149-9
Subject(s) - cytochrome c oxidase , rhodobacter sphaeroides , heme , cytochrome , chemistry , cytochrome c1 , mutant , cytochrome c , cytochrome c peroxidase , biochemistry , stereochemistry , coenzyme q – cytochrome c reductase , enzyme , gene , photosynthesis , mitochondrion
Wild‐type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides were characterized by EPR spectroscopy. A pH‐induced g 12 signal, seen previously in mammalian cytochrome oxidase and assigned to the presence of a bridging car☐yl ligand in the bimetallic cytochrome a 3 ‐Cu B site, is found also in the bacterial enzyme. Mutation of glutamate‐286 to glutamine inactivates the enzyme but does not affect this signal, demonstrating that the car☐yl group of this residue is not the bridging ligand. Three mutants, M106Q, located one helix turn below a histidine ligand to cytochrome a , and T352A as well as F391Q, located close to the bimetallic center, are shown to affect dramatically the low‐spin heme signal of cytochrome a . These mutants are essentially inactive, suggesting that these three mutations result in alterations to cytochrome a that render the oxidase non‐functional.