The respiratory arsenate reductase from Bacillus selenitireducens strain 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 µM and V_max of 2.5 µmol 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 fr which was cloned and sequenced) indicate it is a member of the DMSO reductase family of molybdoproteins.