A bovine mtDNA-binding protein to a conserved sequence adjacent to the termination associated sequence in the vertebrate mitochondrial displacement loop region.

We have found a sequence-specific mitochondrial (mt) DNA-binding protein in bovine mitochondria. The binding site designated Mt5 is adjacent to the termination associated sequence in the vertebrate mt displacement loop region and is interspecifically conserved. An UV-crosslinking and gel filtration demonstrated that a Mt5-binding protein (designated Mt5BP) exists in the mitochondria as a homodimer of an approximately 97-kDa polypeptide. The nucleotide sequence of Mt5 is homologous to that of the binding site for the recently reported mt pause-region binding protein (mtPBP) 1 from sea urchin embryo mitochondria. Gel mobility shift competition experiments indicated that Mt5BP can recognize human sequence couterparts for the mtPBP1-binding site. These results suggest that Mt5BP is related to mtPBP1 with respect to discontinuance of heavy-strand synthesis.