title: Substrate recognition by the Lyn protein-tyrosine kinase. NMR structure of the immunoreceptor tyrosine-based activation motif signaling region of the B cell antigen receptor.
abstract: The immunoreceptor tyrosine-based activation motif (ITAM) plays a central role in transmembrane signal transduction in hematopoietic cells by mediating responses leading to proliferation and differentiation. An initial signaling event following activation of the B cell antigen receptor is phosphorylation of the CD79a (Ig-alpha) ITAM by Lyn, a Src family protein-tyrosine kinase. To elucidate the structural basis for recognition between the ITAM substrate and activated Lyn kinase, the structure of an ITAM-derived peptide bound to Lyn was determined using exchange-transferred nuclear Overhauser NMR spectroscopy. The bound substrate structure has an irregular helix-like character. Docking based on the NMR data into the active site of the closely related Lck kinase strongly favors ITAM binding in an orientation similar to binding of cyclic AMP-dependent protein kinase rather than that of insulin receptor tyrosine kinase. The model of the complex provides a rationale for conserved ITAM residues, substrate specificity, and suggests that substrate binds only the active conformation of the Src family tyrosine kinase, unlike the ATP cofactor, which can bind the inactive form.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-1333, USA.
authors.forename: B S
authors.initials: BS
authors.lastname: Gaul
authors.forename: M L
authors.initials: ML
authors.lastname: Harrison
authors.forename: R L
authors.initials: RL
authors.lastname: Geahlen
authors.forename: R A
authors.initials: RA
authors.lastname: Burton
authors.forename: C B
authors.initials: CB
authors.lastname: Post
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology*; D001665:Binding Sites; D051925:CD79 Antigens; D016384:Consensus Sequence; D004789:Enzyme Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010766:Phosphorylation; D011972:Receptor, Insulin / Q000737:chemistry; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D051925:CD79 Antigens; D010446:Peptide Fragments; D011947:Receptors, Antigen, B-Cell; D011972:Receptor, Insulin; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases