S-Nitrosylation is a two-sided and dynamic post-translational modification of cysteine thiol side chains by nitric oxide of proteins of the redox-based modification that subserves a number of important cellular functions. Nowadays, it has become obvious that S-nitrosylation of key Cys residues on proteins mediates a multitude of cellular processes, including signaling, metabolism, and stress responses. The popular cellular influence of nitric oxide (NO) is brought into play substantially through protein S-nitrosylation.