ABSTRACT
Zinc is important for virtually all aspects of cellular functions. Two recent developments signi cantly advanced our understanding of human zinc biology: the recognition that zinc is a constituent of several thousand proteins and the discoveries that cellular zinc homeostasis requires at least three dozen proteins and a high degree of regulation and integration into cellular signaling networks. This chapter focuses on yet another development, namely emerging general and cell-speci c functions of zinc ions beyond their roles in established zinc proteins. How zinc is controlled in human cells will be the basis for discussing the functions of zinc ions in cellular regulation and signal transduction, especially in phosphorylation cascades, and their transient interactions with some proteins that are generally not recognized as zinc proteins. Comparative and speci c aspects of the zinc biology in plants, single-cell eukaryotes, or microorganisms are beyond the scope of this chapter. New functions of zinc can be summarized under a role of zinc ions as intercellular and intracellular signals, although they embody quite different principles of action. In essence, these functions establish additional biological activities and a much broader role of zinc in biology than previously acknowledged.
