On the Effect of Cholesterol on the Fate of CYP11A1 Imported into Yeast Mitochondria in vivo

I. E. Kovaleva, S. I. Grivennikov, and V. N. Luzikov^*

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-3181; E-mail: luzikov@genebee.msu.su

^* To whom correspondence should be addressed.

Received February 28, 2000; Revision received March 15, 2000

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It has earlier been shown that CYP11A1 (cytochrome P450scc precursor), synthesized in yeast cells, is imported into yeast mitochondria. However, in large part the foreign protein undergoes degradation or aggregates. In this work, we tried to prevent aggregation of CYP11A1 and stimulate its insertion into the mitochondrial inner membrane by substituting cholesterol (a substrate for cytochrome P450scc) for ergosterol in yeast cells. To this end, an ergosterol-deficient Saccharomyces cerevisiae mutant, growing in the presence of cholesterol and expressing a modified bovine CYP11A1 gene, was used. Under defined conditions, the mitochondrial respiratory system developed in this yeast and CYP11A1 with the CoxIV targeting presequence was imported into the mitochondria, being then proteolytically processed. However, substitution of cholesterol for ergosterol did not result in lowered aggregation of the imported CYP11A1 and its increased content in the SMP fraction. Hence, the presence of cholesterol is not instrumental in proper intramitochondrial compartmentalization and folding of CYP11A1.

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KEY WORDS: cytochrome P450scc (CYP11A1), cholesterol, yeast mitochondria, import, compartmentalization, aggregation

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