Component of the perchlorate reductase that catalyzes the reduction of perchlorate to chlorite and allows anaerobic growth on perchlorate as the sole electron acceptor. Is probably also able to reduce chlorate to chlorite. The alpha subunit is likely the catalytic subunit. Binds 1 [4Fe-4S] cluster. Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Heterotrimer of alpha, beta and gamma subunits. Transcription of pcrA occurs only under anaerobic (per)chlorate-reducing conditions. The presence of oxygen completely inhibits pcrA expression regardless of the presence of perchlorate, chlorate, or nitrate. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Deletion of the pcrA gene abolishes anaerobic growth in both perchlorate and chlorate but not in nitrate, indicating that the pcrABCD genes play a functional role in perchlorate reduction separate from nitrate reduction. Deletion mutant strains are still able to grow aerobically. 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. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.