RESCUE OF YEAST DEFECTIVE IN MITOCHONDRIAL ATP SYNTHASE SUBUNIT-8 BY A HETEROLOGOUS GENE FROM ASPERGILLUS-NIDULANS

Mitochondrial ATP synthase subunit 8 of the yeast Saccharomyces cerevi siae and of the filamentous fungus Aspergillus nidulans have the same length and similar structural motifs. However,the two proteins share o nly 50% identical residues, with the conserved residues being concentr ated in the N- and C-terminal domains. We have investigated whether it is amino acid sequence or overall structural motifs that are required for subunit and function. PCR was used to construct a gene encoding A . nidulans subunit 8 fused to an N-terminal cleavable mitochondrial ta rgeting sequence. Following expression in the nucleus of a yeast strai n deficient in subunit 8, the chimaeric precursor targeted the subunit 8 protein back to the mitochondrion. The A. nidulans subunit 8 was fo und to be able to restore growth on non-fermentable substrate at 18 de grees C and 28 degrees C, but not at 36 degrees C. Given the sequence divergence between subunit 8 of A. nidulans and that of S. cerevisiae, this finding suggests that common structural motifs are important for subunit 8 function. (C) 1994 Academic Press, Inc.