Bhattacharjee H, Rosen B P
Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA.
J Biol Chem. 1996 Oct 4;271(40):24465-70. doi: 10.1074/jbc.271.40.24465.
ArsA ATPase activity is allosterically activated by salts of the semimetal arsenic or antimony. Activation is associated with the presence of three cysteine residues in ArsA: Cys113, Cys172, and Cys422. To determine the distance between cysteine residues, wild type ArsA and ArsA proteins with cysteine to serine substitutions were treated with the bifunctional alkylating agent dibromobimane, which reacts with thiol pairs within 3-6 A of each other to form a fluorescent adduct. ArsA proteins in which single cysteine residues were altered by site-directed mutagenesis still formed fluorescent adducts. Proteins in which two of the three cysteine residues were substituted did not form fluorescent adducts. These results demonstrate that Cys113, Cys172, and Cys422 are in close proximity of each other. We propose a model in which As(III) or Sb(III) interacts with these three cysteines in a trigonal pyramidal geometry, forming a novel soft metal-thiol cage.
ArsA ATP酶活性受到半金属砷或锑的盐的变构激活。激活与ArsA中三个半胱氨酸残基的存在有关：Cys113、Cys172和Cys422。为了确定半胱氨酸残基之间的距离，用双功能烷基化剂二溴联苯胺处理野生型ArsA和半胱氨酸被丝氨酸取代的ArsA蛋白，该试剂与彼此距离在3 - 6埃内的硫醇对反应形成荧光加合物。通过定点诱变改变单个半胱氨酸残基的ArsA蛋白仍形成荧光加合物。三个半胱氨酸残基中有两个被取代的蛋白不形成荧光加合物。这些结果表明Cys113、Cys172和Cys422彼此非常接近。我们提出一个模型，其中As(III)或Sb(III)以三角锥几何形状与这三个半胱氨酸相互作用，形成一个新型的软金属 - 硫醇笼。
