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 from Methanobacterium thermoautotrophicum delta H was cloned, and its nucleotide sequence was determined. The gene for A2, designated atwA, encodes an acidic protein of 59,335 Da. Amino acid sequence analysis revealed partial homology of A2 to a number of eucaryotic and bacterial proteins in the ATP-binding cassette (ABC) family of transport systems. Component A2 possesses two ATP-binding domains. A 2.2-kb XmaI-BamHI fragment containing atwA and the surrounding open reading frames was cloned into pGEM-7Zf(+). A cell extract from this strain replaced purified A2 from M. thermoautotrophicum delta H in an in vitro methylreductase assay.