Role of amino acid residues surrounding the phosphorylation site in peptide substrates of G protein-coupled receptor kinase 2 (GRK2).

A series of amino acid substitutions was made in a previously identified β-tubulin-derived GRK2 substrate peptide (404 DEMEFTEAESNMN416 ) to examine the role of amino acid residues surrounding the phosphorylation site. Anionic amino acid residues surrounding the phosphorylation site played an important role in the affinity for GRK2. Compared to the original peptide, a modified peptide (Ac-EEMEFSEAEANMN-NH2 ) exhibited markedly higher affinity for GRK2, but very low affinity for GRK5, suggesting that it can be a sensitive and selective peptide for GRK2.