Helmann J D, Ballard B T, Walsh C T
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Science. 1990 Feb 23;247(4945):946-8. doi: 10.1126/science.2305262.
Bacterial MerR proteins are dimeric DNA-binding proteins that mediate the Hg(II)-dependent induction of mercury resistance operons. Site-directed mutagenesis of the Bacillus sp. RC607 MerR protein reveals that three of four Cys residues per monomer are required for Hg(II) binding at the single high-affinity binding site. Inactive mutant homodimers can exchange subunits to form heterodimers active for Hg(II) binding. Studies of a heterodimer retaining only three of eight cysteine residues per dimer reveal that Cys79 in one subunit and Cys114 and Cys123 in the second subunit are necessary and sufficient for high-affinity Hg(II) binding in an asymmetric, subunit bridging coordination complex.
细菌MerR蛋白是二聚体DNA结合蛋白，介导汞抗性操纵子的汞（II）依赖性诱导。对芽孢杆菌属RC607 MerR蛋白进行定点诱变表明，每个单体的四个半胱氨酸残基中有三个是在单个高亲和力结合位点结合汞（II）所必需的。无活性的突变体同二聚体可以交换亚基以形成对汞（II）结合有活性的异二聚体。对每个二聚体仅保留八个半胱氨酸残基中的三个的异二聚体的研究表明，一个亚基中的Cys79以及第二个亚基中的Cys114和Cys123对于在不对称的亚基桥联配位复合物中进行高亲和力汞（II）结合是必要且充分的。
