D-amino acid residues as substrate specificity determinants for casein kinase II

A set of diastereomeric peptides RRRDDDSDDD each with a corresponding D-amino acid residue successively in every position (except the arginines) was tested as substrates for casein kinase II. It was found that the D-serine containing peptide was not detectably phosphorylated. The replacements at the positions +1, -1 and +2 decreased the kII values more than 60, 30 and 20 times, respectively. The effect of the L/D replacements decreased with increased distance from the serine. The D-amino acid scan used herein seems to be a helpful complementary tool for studies of substrate specificity determinants for different protein kinases.