ABSTRACT
The cysteinyl thiol exists in a variety of forms in biological systems. Most protein structures contain cysteinyl residues either in the free reduced form and/or in the oxidized disulfide form. 1 The utilization of this redox couple has contributed greatly to the generation of the diverse protein structures and activities in biological systems. Similarly, evolution has made use of the unique chemical properties of this functional group in a number of key low molecular weight, water-soluble molecules such as in the ubiquitous tripeptide glutathione (GSH). 2 The common structural origin of protein thiols (PrSHs) and low molecular weight thiols such as GSH has led to a number of fascinating possibilities of interplay between these biological components. Of particular interest to the present discussion is the various ways in which water-soluble thiols can contribute to the expression of the structure, activity, and regulation of proteins. Such control would be of great evolutionary importance to the organization of protein activities into complex physiological processes and the development of cellular function.
