tailieunhanh - Báo cáo khoa học: Heavy metal ions inhibit molybdoenzyme activity by binding to the dithiolene moiety of molybdopterin in Escherichia coli

Molybdenum insertion into the dithiolene group on the 6-alkyl side-chain of molybdopterin is a highly specific process that is catalysed by the MoeA and MogA proteins in Escherichia coli. Ligation of molybdate to molybdopterin generates the molybdenum cofactor, which can be inserted directly into molybdoenzymes binding the molybdopterin form of the molybdenum cofactor, | ễFEBS Journal Heavy metal ions inhibit molybdoenzyme activity by binding to the dithiolene moiety of molybdopterin in Escherichia coli Meina Neumann and Silke Leimkuhler Department of Proteinanalytics Institute of Biochemistry and Biology University of Potsdam Germany Keywords copper dithiolene metal toxicity Moco molybdenum Correspondence S. Leimkuhler Institute of Biochemistry and Biology University of Potsdam D-14476 Potsdam Germany Fax 49 331 977 5128 Tel 49 331 977 5603 E-mail sleim@ Received 15 July 2008 revised 3 September 2008 accepted 19 September 2008 doi Molybdenum insertion into the dithiolene group on the 6-alkyl side-chain of molybdopterin is a highly specific process that is catalysed by the MoeA and MogA proteins in Escherichia coli. Ligation of molybdate to molybdopterin generates the molybdenum cofactor which can be inserted directly into molybdoenzymes binding the molybdopterin form of the molybdenum cofactor or is further modified in bacteria to form the dinucleotide form of the molybdenum cofactor. The ability of various metals to bind tightly to sulfur-rich sites raised the question of whether other metal ions could be inserted in place of molybdenum at the dithiolene moiety of molybdopterin in molybdoenzymes. We used the heterologous expression systems of human sulfite oxidase and Rhodobacter sphaeroides dimethylsulfoxide reductase in E. coli to study the incorporation of different metal ions into the molybdopterin site of these enzymes. From the added metal-containing compounds Na2MoO4 Na2WO4 NaVO3 Cu NO3 2 CdSO4 and NaAsO2 during the growth of E. coli only molybdate and tungstate were specifically inserted into sulfite oxidase and dimethylsulfoxide reductase. Other metals such as copper cadmium and arsenite were nonspecifically inserted into sulfite oxidase but not into dimethylsulfoxide reductase. We showed that metal insertion into molybdopterin occurs beyond the step of molybdopterin .