QcrCAB operon of a nocardia-form actinomycete Rhodococcus rhodochrous encodes cytochrome reductase complex with diheme cytochrome cc subunit.

Structural genes encoding quinol-cytochrome c reductase (QcR) were cloned and sequenced from nocardia-form actinomycete Rhodococcus rhodochrous. QcrC and qcrA encode diheme cytochrome cc and the Rieske Fe-S protein, respectively, while the qcrB product is a diheme cytochrome b. These amino acid sequences are similar to those of Corynebacterium and Mycobacterium, the members of high G+C content firmicutes.