Reactive cysteine in proteins Protein folding, antioxidant defense, redox signaling and more

ABSTRACT

Cysteine plays structural roles in proteins and can also participate in electron transfer reactions, when some structural folds provide appropriatedenvironments for stabilization of its sulfhydryl group in the anionic form, called thiolate (RS−). In contrast, sulfhydryl group of free cysteine has arelatively high pKa (8,5) and as a consequence is relatively inert for redox reaction in physiological conditions. Thiolate is considerable morepowerful as nucleophilic agent than its protonated form, therefore, reactive cysteine are present mainly in its anionic form in proteins. In this review,we describe several processes in which reactive cysteine in proteins take part, showing a high degree of redox chemistry versatility.