Nuclear genes coding the yeast mitochondrial adenosine triphosphatase complex. Primary sequence analysis of ATP2 encoding the F1-ATPase beta-subunit precursor.

The yeast nuclear gene ATP2 encodes a F1-ATPase beta-subunit protein of 509 amino acids with a predicted mass of 54,575 daltons. In contrast to the ATPase beta-subunit proteins determined previously from Escherichia coli and various plant sources, the yeast mitochondrial precursor peptide contains a unique cysteine residue within its immediate amino terminus. Expression of an in-frame deletion in ATP2 between residues 28 and 34 to eliminate this single cysteine residue located near the processing site of the matrix protease does not prevent the in vivo delivery of the subunit to mitochondria or its assembly into a functional ATPase complex. Thus, the import F1 beta-subunit into mitochondria does not require a covalent modification of the type utilized for the secretion of the major lipoprotein from E. coli. In addition, analysis of the level of the major F1-ATPase subunits in mitochondria prepared from an atp2- disruption mutant demonstrates that the in vivo import of these catalytic subunits is not dependent on each other. These data and additional studies, therefore, suggest that the determinants for mitochondrial delivery reside within the amino terminus of the individual precursors.