Binding of tyrosine hydroxyl groups

The binding of a hormone or growth factor (a ligand) to a dimeric receptor activates the protein kinase domain of the receptor which phosphorylates a number of tyrosine hydroxyl groups of the receptor itself. This autophosphorylation is followed by a variety of events, which include phosphorylation of tyrosine side chains of various other proteins.426 An-... 

A new motif for OP binding to tyrosine has been identified. Almost all proteins appear to be capable of binding OP covalently on tyrosine. Whether or not OP will bind to tyrosine in vivo will depend on the concentration of the protein, the concentration of the OP, and the ionization status of the tyrosine hydroxyl group. The latter factor appears to be dependent on the presence of nearby positively charged residues. 

The catalytically essential nature of tyrosine 85 and its proximity to the substrate binding site and to tyrosine 115 were demonstrated from studies of modification with tetranitromethane (71) and from studies of intramolecular cross-linking of aminotyrosyl residues (72). The bro-moacetamidophenyl (69) and diazonium (70) reagents obtained from aminophenyl-pdT both react selectively and exclusively with tyrosine 85. This residue is situated, stereochemically, such that its hydroxyl group can interact with the 3 -phosphate of pdTp. 

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