| Abstract: | Three proteins of the inner mitochondrial membrane of Neurospora crassa were found to be covalently modified with a derivative of pantothenic acid. One of these proteins is a subunit of cytochrome c oxidase and two are subunits of the ATPase-ATP synthase. Cells of a pantothenate auxotroph of N. crassa were labeled with 14C]pantothenic acid, and mitochondrial proteins containing radiolabeled pantothenate were detected by electrophoresis of detergent-solubilized mitochondria. Mitochondria from cells that were colabeled with 14C]pantothenate and 3H]leucine were reacted with specific antisera against the cytochrome c oxidase and F1-ATPase enzyme complexes. Electrophoresis of the labeled subunits of these isolated complexes showed that the 14C]pantothenate-associated peptides corresponded to 3H]leucine-labeled subunit 6 of cytochrome c oxidase and two 3H]leucine-labeled subunits (tentatively identified as subunits 8 and 11) of the ATPase-ATP synthase. Pantothenate modification of these enzyme subunits, which are synthesized on extramitochondrial ribosomes, may contribute to their transport and assembly into mitochondria, or it may participate in the catalytic activity of the assembled enzymes. |
