Effects of mutation of residue I67 on redox-linked protonation processes in yeast cytochrome c oxidase.
We describe effects of a mutation, Ile-67-->Asn, in subunit I of yeast cytochrome c oxidase on redox-linked protonation processes within the protein. The mutation lowers the midpoint potential of haem a and weakens its pH dependency, but has little effect on the potential of haem a3. The residue is close to a conserved glutamate (Glu-243) in the crystal structure. We propose that protonation of Glu-243 is redox-linked to haem a, that Asn-167 perturbs its pK and that redox-linked protonation in this location is essential for the catalytic reactions of the binuclear centre. These proposals are discussed in terms of a 'glutamate trap' mechanism for proton translocation in the haem/copper oxidases.
Meunier
B
B
Glynn Laboratory of Bioenergetics, Department of Biology, University College London, Gower Street, London WC1E 6BT, U.K.
Ortwein
C
C
Brandt
U
U
Rich
P R
PR
D001216:Asparagine; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D018698:Glutamic Acid; D006418:Heme / Q000031:analogs & derivatives / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007532:Isoleucine; D007700:Kinetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017354:Point Mutation; D011199:Potentiometry; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D046911:Macromolecular Substances; D011994:Recombinant Proteins; D007532:Isoleucine; C027728:heme a; D018698:Glutamic Acid; D006418:Heme; D001216:Asparagine; D003576:Electron Transport Complex IV