Nitric oxide is a second messenger in the regulation of various physiological functions. Additionally, nitric oxide reacts rapidly with superoxide anion radical to form peroxynitrite anions, which are capable of nitrating aromatic compounds. The src homology-2(SH2) domains are modules of about 100 amino acid residues that are found in phosphoinositide-specific phospholipase C type (PLC-gamma) and other intracellular signal transduction proteins. They bind specifically to phosphotyrosine-containing cellular proteins. The real time biospecific interaction analysis (BIAcore system) was used to determine the binding of the SH2 domains of PLC-gamma and its SH2 recognizable binding sites. The specific synthetic polypeptide containing tyrosine-phosphorylated amino acid sequences of ENAEYLDLDC and CGDNDYIIPL can bind to the N-terminal and the C-terminal of SH2 domains of PLC-gamma, respectively. However, neither unphosphorylated nor nitrated peptides can bind to SH2 domains. By using Guggenhein's method, we analyzed the results obtained from the BIAcore system and found that the binding affinity of the C-terminal (kd=0.33 mictoM) and N-terminal (kd=0.2 microM)of SH2 domains of PLC-gamma to the specific tyrosine phosphorylated peptide were very similar.
