Mapping the cysteine proteome: analysis of redox-sensing thiols.

The cysteine (Cys) proteome includes 214,000 Cys with thiol and other forms. A relatively small subset functions in cell signaling, while a larger number coordinate cell functions in response to redox state. The former are redox-signaling thiols while the latter are defined as redox-sensing thiols. Bulk measurements are not very informative for systems biology because reactivity of thiols in proteins differs by seven orders of magnitude. Proteomic databases contain annotation of Cys, for example, disulfides and zinc fingers, but do not include quantitative information necessary to develop functional models. Complementary databases and Cys proteome maps are needed to describe thiol redox circuits and connect these to functional redox-dependent pathways. This article summarizes progress in quantitative redox proteomics to develop such maps.