Phosphorylated sites in substrates of intracellular protein kinases: a common feature in amino acid sequences.

Examination of the primary amino acid sequences surrounding phosphorylated sites in many intracellular phosphoproteins indicated that the phosphorylated hydroxyamino acid (either serine or threonine) is, in general, surrounded by amino acids having a positively charged side chain and, more specifically, is frequently separated from a basic amino acid (either lysine or arginine) by only one amino acid. Possible reasons for this common feature are discussed.