Advances in the structure and chemistry of metallothioneins

A low molecular weight (6-7 kDa) class of metalloproteins, designated as metallothioneins (MTs), exhibit repeated sequence motifs of either CxC or CxxC through which mono or divalent d(10) metal ions are bound in polymetallic-thiolate clusters. The preservation of metal-thiolate clusters in an increasing number of three-dimensional structures of these proteins signifies the importance of this structural motif. This review focuses on the recent developments regarding the versatile and striking chemical reactivity of MTs as well as on the existence of conformational/configurational dynamics within their structure. Both properties and their interplay are likely to be essential for the still elusive biological function of these proteins.