Background
Metallothioneins are ubiquitous small, cysteine-rich, multifunctional proteins which can bind heavy metals. Methodology/principal findings: We report the
Significance
The small number and remarkably regular structure of Tetrahymena MTs, coupled with the experimental tractability of this model organism for studies of in vivo function, make it an attractive system for the experimental dissection of the roles, structure/function relationships, regulation of gene expression, and adaptive evolution of these proteins, as well as for the development of biotechnological applications for the environmental monitoring of toxic substances.