Arsenic methylation by a novel ArsM As(III) S‐adenosylmethionine methyltransferase that requires only two conserved cysteine residues

• DOI: 10.1111/mmi.13882
• Publication Date: 2017-11-14T06:45:50Z
• Authors: Ke Huang; Yan Xu; Charles Packianathan; Fan Gao; Chuan Chen; Jun Zhang; Qirong Shen; Barry P. Rosen; Fang‐Jie Zhao
• Keywords: Conserved sequence; Heterologous expression

Summary Arsenic (As) biomethylation is an important component of the As biogeochemical cycle that can influence toxicity and mobility in environment. Biomethylation catalyzed by enzyme arsenite (As[III]) S ‐adenosylmethionine methyltransferase (ArsM). To date, all identified ArsM orthologs with As(III) methylation activities have four conserved cysteine residues, which are thought to be essential for methylation. Here, we isolated As(III)‐methylating bacterium, Bacillus sp. CX‐1, a gene encoding methyltranserase termed BlArsM low sequence similarities (≤ 39%) other ArsMs. has six residues (Cys10, Cys11, Cys145, Cys193, Cys195 Cys268), three Cys145 Cys195) align found most BlarsM constitutively expressed CX‐1. Heterologous expression conferred resistance. Purified methylated both methylarsenite (MAs[III]), final product dimethylarsenate (DMAs[V]). When cysteines were individually altered serine only C145S C195S derivatives lost ability methylate MAs(III). The derivative C10S/C11S/C193S/C268S was still active. These results suggest novel requiring two residues. A model proposed.