Similar genes for a mitochondrial ATPase subunit in the nuclear and mitochondrial genomes of Neurospora crassa.

Abstract

The proton-translocating ATPases from mitochondria, chloroplasts and bacteria consist of ∼10 different polypeptide subunits1. The smallest subunit, a proteolipid of molecular weight ∼8,000, is present in a stoichiometric amount of six—these six polypeptides are thought to form a proton channel through the membrane2. The proteolipid is affected by the ATPase inhibitors oligomycin and dicyclohexylcarbodiimide (DCCD). As DCCD is covalently bound to it, the proteolipid is commonly referred to as the DCCD-binding protein. Because of the spatial arrangement of the proteolipids in the membrane, binding is probably restricted to one specific glutamic acid residue2,3. In the yeast Saccharomyces cerevisiae the DCCD-binding protein is encoded by the mitochondrial DNA and synthesized inside the mitochondria4, whereas in Neurospora crassa, another ascomycete, the gene for the DCCD-binding protein lies in the nucleus, and the protein is synthesized outside the mitochondria5. Here we report the presence on the mitochondrial DNA of N. crassa of a nucleotide sequence which potentially encodes another DCCD-binding protein. Although a translation product has not yet been found, we suggest a possible function of this gene and speculate on its evolutionary origin.