B.E. Kemp, R.B. Pearson, "Protein kinase recognition sequence motifs," Trends in Biochemical Sciences, 15:342-46, 1990.
Bruce Kemp (St. Vincent's Institute, Melbourne, Australia): "It is now clear that protein phosphorylation is the most widespread mechanism for modulation of protein function known and that it regulates all physiological processes within living cells. Protein kinases constitute one of the largest families of regulatory proteins and include many hormone receptors, calcium-regulated protein kinases, lipid- and phospholipid-dependent protein kinases, and protein kinases that are themselves regulated by protein phosphorylation.
"The substrate specificity of these enzymes is vitally important in the coordinated control, determining which proteins are phosphorylated and at what sites. This is especially important in cases in which proteins are multi-phosphorylated by protein kinases involved in different signal-transduction pathways.
"In many instances, but not all, the local amino acid sequence around the phosphorylation site in the substrate protein acts as a recognition motif.