A PROTEIN WHICH BINDS PREFERENTIALLY TO SINGLE-STRANDED CORE SEQUENCEOF AUTONOMOUSLY REPLICATING SEQUENCE IS ESSENTIAL FOR RESPIRATORY-FUNCTION IN MITOCHONDRIA OF SACCHAROMYCES-CEREVISIAE

From yeast nuclear extract, we have identified several DNA-protein com plexes using the T-rich strand of core consensus sequence of autonomou sly replicating sequence by gel shift assay. One of them showed prefer ential binding to the T-rich sequence of the DNA. We have partially pu rified a protein constituent of this complex and cloned its gene. The gene has an open reading frame encoding a protein of 380 amino acids ( M(r) = 42,100) which is processed to a mature protein of 371 amino aci ds (M(r) = 40,900). The protein has neither significant amino acid hom ology with any previously reported proteins nor characteristic motifs. A putative HAP2/HAP3/HAP4 binding sequence was found at about 1 kilob ase upstream of the gene. Disruption of the chromosomal gene revealed that the gene was neither essential for cell viability nor involved in DNA replication, but was essential for mitochondrial respiratory func tion. We therefore named the gene MRF1 for mitochondrial respiratory f unction 1. In a mrf1 null mutant the absorption spectra of cytochromes b, a, and a(3) were undetectable, although mitochondrial DNA and prot ein synthesis in mitochondria were intact. Antibodies against MRF1 det ected the antigen localized predominantly in the nucleus in vivo. Thes e results suggest that MRF1 is a transcriptional regulatory protein of some genes whose products are necessary for the functional assembly o f mitochondrial respiratory proteins.