A gene coding for aa3 subunit I is obtained from a Corynebacterium
glutamicum chromosomal DNA library by hybridization utilizing a probe
produced based on a sequence common to a wide range of heme-copper
enzymes. A gene coding for subunit II and a gene coding for subunit III
are obtained by hybridization using a probe produced by using primers
prepared based on the N-terminus amino acid sequence of subunit II, which
is determined by using purified cytochrome aa3, and an operon coding for
cytochrome bc1 complex existing downstream from the foregoing genes is
further obtained.