Open AccessPurification and analysis of phospholipids in the inner mitochondrial membrane fraction of bovine corpus luteum, and properties of cytochrome P‐450 scc incorporated into vesicles prepared from these phospholipids
Author(s) -
TUCKEY Robert C.,
STEVENSON Patricia M.
Publication year - 1985
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1985.tb08849.x
Subject(s) - cardiolipin , corpus luteum , phospholipid , phosphatidylethanolamine , phosphatidylcholine , inner mitochondrial membrane , cytochrome , vesicle , biochemistry , inner membrane , biology , cytochrome c , cholesterol , chemistry , mitochondrion , membrane , enzyme , hormone
Cytochrome P‐450 scc , which catalyses the conversion of cholesterol to pregnenolone in steroidogenic tissues, can be incorporated into artificial phospholipid vesicles and cholesterol binding to the cytochrome is affected by the composition of the vesicles. We have purified the phospholipids from the inner mitochondrial membrane fraction of the bovine corpus luteum where the cytochrome is located. The composition in mol % was 49% phosphatidylcholine, 34% phosphatidylethanolamine, 8.7% cardiolipin, 6.4% lysophosphatidylethanolamine and 1.5% phosphatidylinositol. The ratio of cholesterol to phospholipid (mol/mol) in the inner membrane fraction was 0.14 to 1. The K m for cholesterol of purified luteal cytochrome P‐450 scc incorporated into vesicles prepared from the total inner mitochondrial membrane phospholipids was 0.063 mol of cholesterol per mol of phospholipid. Removal of the cardiolipin component of the inner mitochondrial membrane phospholipids prior to preparation of vesicles caused a four fold increase in the K d of cytochrome P‐450 for cholesterol and a two fold increase in K m . The data suggests that in the inner mitochondrial membrane of the bovine corpus luteum the cholesterol concentration is less than saturating for cytochrome P‐450 scc .