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Two metallothionein (MT) isoforms have been identified in the model nem-atode Caenorhabditis elegans: CeMT1 and CeMT2, comprising two poly-peptides that are 75 and 63 residues in length, respectively. Both isoforms encompass a conserved cysteine pattern (19 in CeMT1 and 18 in CeMT2) and, most significantly | Caenorhabditis elegans metallothionein isoform specificity - metal binding abilities and the role of histidine in CeMTI and CeMT2 Roger Bofill1 Ruben Orihuela1 Miriam Romagosa2 Jordi Domènech2 Silvia Atrian2 and Merce Capdevila1 1 Departament de Quimica Facultat de Ciencies Universitat Autonoma de Barcelona Spain 2 Departament de Genetica Facultat de Biologia Universitat de Barcelona and IBUB Institut Biomedicina de la Universitat de Barcelona Spain Keywords Caenorhabditis elegans differentiation isoform specificity metal-histidine coordination metallothionein Correspondence S. Atrian Departament de Genetica Facultat de Biologia Universitat de Barcelona Avinguda Diagonal645 08028 Barcelona Spain Fax 34 93 4034420 Tel 34 93 4021501 E-mail satrian@ub.edu These authors contributed equally to this work Received 15 May 2009 revised 17 September 2009 accepted 30 September 2009 doi 10.1111 j.1742-4658.2009.07417.x Two metallothionein MT isoforms have been identified in the model nematode Caenorhabditis elegans CeMT1 and CeMT2 comprising two polypeptides that are 75 and 63 residues in length respectively. Both isoforms encompass a conserved cysteine pattern 19 in CeMT1 and 18 in CeMT2 and most significantly as a result of their coordinative potential CeMT1 includes four histidines whereas CeMT2 has only one. In the present study we present a comprehensive and comparative analysis of the metal Zn II Cd II and Cu I binding abilities of CeMT1 and CeMT2 performed through spectroscopic and spectrometric characterization of the recombinant metal-MT complexes synthesized for wild-type isoforms CeMTI and CeMT2 their separate N- and C-terminal moieties NtCeMTl CtCeMTI NtCeMT2 and CtCeMT2 and a AHisCeMT2 mutant. The corresponding in vitro Zn Cd- and Zn Cui-replacement and acidification7 renaturalization processes have also been studied as well as protein modification strategies that make it possible to identify and quantify the contribution of the histidine residues to metal .
