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Evidence for noncooperative metal binding to the α domain of human metallothionein
Author(s) -
Rigby Duncan Kelly E.,
Stillman Martin J.
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05762.x
Subject(s) - metallothionein , chemistry , metal , reactivity (psychology) , titration , stereochemistry , inorganic chemistry , zinc , organic chemistry , medicine , alternative medicine , pathology
In the present study, we investigated the metal‐binding reactivity of the isolated α 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 α domain with Cd 2+ 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 Cd 2+ conditions. Titration with four molar equivalents of Cd 2+ was required for the formation of the Cd 4 α 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.