COMPONENT-A2 OF METHYLCOENZYME-M REDUCTASE SYSTEM FROM METHANOBACTERIUM-THERMOAUTOTROPHICUM DELTA-H - NUCLEOTIDE-SEQUENCE AND FUNCTIONAL EXPRESSION BY ESCHERICHIA-COLI

The gene for component A2 of the methylcoenzyme M reductase system fro m Methanobaterium thermoautotrophicum DELTAH was cloned, and its nucle otide sequence was determined. The gene for A2, designated atwA, encod es an acidic protein of 59,335 Da. Amino acid sequence analysis reveal ed partial homology of A2 to a number of eucaryotic and bacterial prot eins in the ATP-binding cassette (ABC) family of transport systems. Co mponent A2 possesses two ATP-binding domains. A 2.2-kb XmaI-BamHI frag ment containing atwA and the surrounding open reading frames was clone d into pGEM-7Zf(+). A cell extract from this strain replaced purified A2 from M. thermoautotrophicum DELTAH in an in vitro methylreductase a ssay.