The Mhr1 protein is necessary for mtDNA homologous recombination in Saccharomyces cerevisiae. Homologous pairing (HP) is an essential reaction during homologous recombination, and is generally catalyzed by the RecA⁄Rad51 family of proteins in an ATP-dependent manner. Mhr1 cata-lyzes HP through a mechanism similar, at the DNA level, to that of the RecA⁄Rad51 proteins, but without utilizing ATP.