A pantothenate derivative is covalently bound to mitochondrial proteins in Neurospora crassa

Abstract

The presence of protein‐bound pantothenate in Neurospora crassa was investigated by labelling a pantothenate auxotroph (pan‐2) with [14C]pantothenate and examining mycelial homogenates on dodecyl sulfate/polyacrylamide gels. Five peaks of radioactivity were found, with apparent molecular masses of 200, 140, 22, 19, and 9 kDa. The 200‐kDa peak was identified as fatty acid synthetase, based on its absence in a fatty acid synthetase mutant. The 22‐kDa and 19‐kDa peaks co‐purified with mitochondrial markers on sucrose gradients. When purified mitochondria were fractionated, the 19‐kDa protein was associated with the inner membrane and the 22‐kDa protein was enriched in the soluble mitochondrial fraction. The label was quantitatively recovered from the mitochondrial proteins as 4′‐phosphopantetheine after mild alkaline hydrolysis. Although the function of this post‐translational modification of mitochondrial proteins is not known, several possibilities are discussed: the 4′‐phosphopantetheine may act as a carrier group in an enzymatic reaction, or it may perform a regulatory function as part of an enzyme complex. Copyright © 1985, Wiley Blackwell. All rights reserved