[Structural modifications of proteins induced by nitric oxide]

It is well known for ca. two decades that nitric oxide regulates many life processes both in animals and in plants. The list of processes controlled by NO is steadily expanding, and some of the mechanisms of action of this small molecule are being unravelled and understood. Nitric oxide is exerting its action through addition to the transition metal ions which normally function as protein cofactors; in this way NO regulates, e.g., the activity of cytoplasmic guanyl cyclase. Recently, however, more and more often direct structural modifications of peptidyl amino acid residues are being studied. Particular attention is being paid to the modifications of cysteine (S-nitrosylation) and tyrosine (nitration) residues with respect to their putative signalling functions. It is also known that these modifications are modulating activities of numerous proteins. In this paper we are discussing structural modifications of amino acid residues by NO taking into account the conditions which should be fulfilled to consider their signalling functions. Moreover, we also present available methodologies for their analysis and identifications of modified proteins.