Comparisons of coenzyme Q bound to mitochondrial membrane proteins among different mammalian species

The objective of this study was to elucidate the mechanisms that govern the variations in the rates of mitochondrial superoxide anion radical (O-2(-.) ) generation in different species. The amounts of coenzyme Q (CoQ) associat ed with mitochondrial membrane proteins were compared in five different mam malian species, namely mouse, rat, rabbit, pig, and cow. Micelles of cardia c mitochondria were prepared using Triton X-100 or deoxycholate (DOC) as de tergents, and the micelles containing mitochondrial proteins were sedimente d by sucrose density ultracentrifugation. The amount of CoQ present in both types of micelles varied in different species, whereas alpha-tocopherol, a nother lipoidal molecule in mitochondrial membranes, could not be detected in the micelles of any of these species. The amounts of CoQ bound to mitoch ondrial proteins in DOC micelles were higher in those mammalian species whe re CoQ(10) was the predominant CoQ homologue, and the amounts were found to be inversely correlated with the rate of mitochondrial O-2(-.) generation among different species. Results also indicated that mitochondrial CoQ exis ts in at least two distinct pools, one Of which is associated with the memb rane proteins. The degree of association between CoQ and membrane proteins appears to be a factor determining the rate of mitochondrial O-2(-.) genera tion. (C) 1999 Elsevier Science Inc.