CYTOCHROME-C-OXIDASE FROM EUKARYOTES BUT NOT FROM PROKARYOTES IS ALLOSTERICALLY INHIBITED BY ATP

The activity of reconstituted cytochrome c oxidase from bovine heart b ut not from Rhodobacter sphaeroides is allosterically inhibited by int raliposomal ATP, which binds to subunit IV. The activity of cytochrome c oxidase of wild-type yeast and of a subunit VIa-deleted yeast mutan t, measured with Tween 20-solubilized mitochondria in the presence of an ATP-regenerating system, was also allosterically inhibited by ATP, indicating the validity of this mechanism of ''respiratory control'' i n eucaryotic cytochrome c oxidases (Arnold and Kadenbach, Eur. J. Bioc hem. (1997) 249, 350-354). Deletion of subunit VIa changes the biphysi c into monophysic kinetics of the yeast enzyme in the presence of ADP. A tenfold higher amount of horse heart cytochrome c, as compared to y east cytochrome c, was required to relieve the ATP inhibition of the y east enzyme.