The respiratory arsenate reductase fromBacillus selenitireducensstrain MLS10

The respiratory arsenate reductase from the Gram-positive, haloalkaliphile, Bacillus selenitireducens strain MLS10 was purified and characterized. It is a membrane bound heterodimer (150 kDa) composed of two subunits ArrA (110 kDa) and ArrB (34 kDa), with an apparent K(m) for arsenate of 34 microM and V(max) of 2.5 micromol min(-1) mg(-1). Optimal activity occurred at pH 9.5 and 150 g l(-1) of NaCl. Metal analysis (inductively coupled plasma mass spectrometry) of the holoenzyme and sequence analysis of the catalytic subunit (ArrA; the gene for which was cloned and sequenced) indicate it is a member of the DMSO reductase family of molybdoproteins.