2.A.1.70.9
ArsK, exporter of arsenite, antimonite, trivalent roxarsone and methylarsenite (Shi et al. 2018). Expression of arsK is induced by arsenite [As(III)], antimonite [Sb(III)], trivalent roxarsone [Rox(III)], methylarsenite [MAs(III)] and arsenate [As(V)], and heterologous expression of ArsK in an arsenic-hypersensitive E. coli strain showed that ArsK is essential for resistance to As(III), Sb(III), Rox(III) and MAs(III) but not to As(V), dimethylarsenite [Dimethyl-As(III)] or Cd(II). ArsK reduces the cellular accumulation of As(III), Sb(III), Rox(III) and MAs(III) but not to As(V) or Dimethyl-As(III). An arsenic regulator gene arsR2 is cotranscribed with arsK, and ArsR2 interacts with the arsR2-arsK promoter region without metalloids but is derepressed by As(III), Sb(III), Rox(III) and MAs(III). Thus, ArsK is an arsenic efflux protein  and is regulated by ArsR2 (Shi et al. 2018).