Document Actions
The isoforms of yeast cytochrome c oxida ... ic properties of the holoenzyme
The isoforms of yeast cytochrome c oxidase subunit V alter the in vivo kinetic properties of the holoenzyme.
36
One of the nuclear-coded subunits of yeast cytochrome c oxidase is specified by a gene family composed of two genes, COX5a and COX5b. These genes are regulated differentially by oxygen and encode isoforms of subunit V, designated Va and Vb, which have only 66% primary sequence identity. Yeast cells require one or the other isoform for a functional cytochrome c oxidase (Trueblood, C. E., and Poyton, R. O. (1987) Mol. Cell Biol. 7, 3520-3526). To determine if these isoforms of subunit V alter the catalytic properties of holocytochrome c oxidase, we have analyzed various aspects of cytochrome c oxidase function in intact yeast cells that produce only one type of isoform. From measurements of room temperature turnover numbers and low temperature rates of ligand binding, single turnover cytochrome c oxidation, and internal electron transfer (heme a oxidation), we have found that isozymes which incorporate the Vb isoform have both higher turnover rates and higher rates of heme a oxidation than isozymes which incorporate Va. These findings support the conclusion that the isoforms of subunit V modulate cytochrome c oxidase activity in vivo and suggest that they do so by altering the rates of one or more intramolecular electron transfer reactions.
Waterland RA, Basu A, Chance B, Poyton RO
The Journal of biological chemistry
1991-03-05 00:00
266
7
4180-6
Carbon Monoxide,Electron Transport,Electron Transport Complex IV,Isoenzymes,Kinetics,Macromolecular Substances,Oxygen,Polarography,Saccharomyces cerevisiae,Spectrum Analysis,Structure-Activity Relationship,Temperature,Isoenzymes,Macromolecular Substances,Carbon Monoxide,Oxygen,Electron Transport Complex IV
Department of Biochemistry and Biophysics, University of Pennsylania, Philadelphia 19104
J. Biol. Chem.
NIGMS GMHL31909
0021-9258
1067
True
1847916
