Component of the perchlorate reductase that catalyzes the reduction of perchlorate to chlorite and allows anaerobic growth on perchlorate as the sole electron acceptor. The gamma subunit may be responsible for electron transfer to the beta subunit PcrB (Probable). Binds 4 heme groups per subunit. Heterotrimer of alpha, beta and gamma subunits. Has potential use in bioremediation of waste sites contaminated with perchlorate, a common component of solid rocket fuel which is a widespread environmental contaminant in water systems in the United States.