TAILIEUCHUNG - Báo cáo khoa học: Evidence for noncooperative metal binding to the a domain of human metallothionein

In the present study, we investigated the metal-binding reactivity of the isolated a domain of human metallothionein isoform 1a, with specific emphasis on resolving the debate concerning the cooperative nature of the metal-binding mechanism. | ỊFEBS Journal Evidence for noncooperative metal binding to the a domain of human metallothionein Kelly E. Rigby Duncan and Martin J. Stillman Department of Chemistry The University of Western Ontario London ON Canada Keywords CD cooperativity metal-dependent protein folding metallothionein MS Correspondence M. J. Stillman Department of Chemistry Chemistry Building The University of Western Ontario London ON Canada N6A 5B7 Fax 1 519 661 3022 Tel 1 519 661 3821 E-mail Website http chem Received 22 December 2006 revised 2 February 2007 accepted 1 March 2007 In the present study we investigated the metal-binding reactivity of the isolated a domain of human metallothionein isoform 1a with specific emphasis on resolving the debate concerning the cooperative nature of the metal-binding mechanism. The metallation reaction of the metal-free a domain with Cd2 was unequivocally shown to proceed by a noncooperative mechanism at physiologic pH by CD and UV absorption spectroscopy and ESI MS. The data clearly show the presence of intermediate partially metallated metallothionein species under limiting Cd2 conditions. Titration with four molar equivalents of Cd2 was required for the formation of the Cd4a species in 100 abundance. The implications of a noncooperative metal-binding mechanism are that the partially metallated and metal-free species are stable intermediates and thus may have a potential role in the currently undefined function of metallothionein. doi Over the past several decades significant advances have been made in the field of protein folding 1-4 . However the direct and specific involvement of metal ions in the folding process of metalloproteins has received far less attention despite the fact that one-third of all known enzymes require metal ions for structural or functional purposes 5 . Post-translational metal-induced protein folding is a vital process that still requires mechanistic .

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