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 .
C0301714
basic amino acid
C0024337
lysine