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 beta subunit may be responsible for electron transfer to the catalytic alpha subunit PcrA (Probable). Binds 1 [3Fe-4S] cluster. Binds 3 [4Fe-4S] clusters. Heterotrimer of alpha, beta and gamma subunits. Probably translocated together with PcrA, which possesses a Tat-type signal. 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.