Target-Selective Protein S-Nitrosylation by Sequence Motif Recognition

Summary S -nitrosylation is a ubiquitous protein modification emerging as a principal mechanism of nitric oxide (NO)-mediated signal transduction and cell function. S -nitrosylases can use NO synthase (NOS)-derived NO to modify selected cysteines in target proteins. Despite proteomic identification of over a thousand S -nitrosylated proteins, few S -nitrosylases have been identified. Moreover, mechanisms underlying site-selective S -nitrosylation and the potential role of specific sequence motifs remain largely unknown. Here, we describe a stimulus-inducible, heterotrimeric S -nitrosylase complex consisting of inducible NOS (iNOS), S100A8, and S100A9. S100A9 exhibits transnitrosylase activity, shuttling NO from iNOS to the target protein, whereas S100A8 and S100A9 coordinately direct site selection. A family of proteins S -nitrosylated by iNOS-S100A8/A9 were revealed by proteomic analysis. A conserved I/L-X-C-X 2 -D/E motif was necessary and sufficient for iNOS-S100A8/A9-mediated S -nitrosylation. These results reveal an elusive parallel between protein S -nitrosylation and phosphorylation, namely, stimulus-dependent posttranslational modification of selected targets by primary sequence motif recognition.