Reciprocal Regulation of Hck Activity by Phosphorylation of Tyr527 and Tyr416 EFFECT OF INTRODUCING A HIGH AFFINITY INTRAMOLECULAR SH2 LIGAND

摘要: The Src family tyrosine kinase Hck possesses two phosphorylation sites, Tyr527 and Tyr416, that affect the catalytic activity in opposite ways. When phosphorylated, residues C-terminal to it are involved an inhibitory intramolecular interaction with SH2 domain. However, this sequence does not conform of high affinity ligand, pYEEI. We mutated YEEI show mutant form cannot be activated by exogenous ligands. SH3 domain is also ligand Nef binds activates YEEI-Hck a similar manner wild-type Hck, indicating disrupting overrides strengthened interaction. other site, autophosphorylation site activation loop. Phosphorylation Tyr416 required for activation. residue alanine characterized its activity. Y416A shows higherK m value peptide lowerV max than autophosphorylated Hck. present evidence cross-talk between loop binding domains.