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HUMAN P56LCK TYROSINE KINASE COMPLEXED WITH PHOSPHOPEPTIDEHUMAN P56LCK TYROSINE KINASE COMPLEXED WITH PHOSPHOPEPTIDE
Structural highlights
DiseaseLCK_HUMAN Severe combined immunodeficiency due to LCK deficiency. Note=A chromosomal aberration involving LCK is found in leukemias. Translocation t(1;7)(p34;q34) with TCRB. FunctionLCK_HUMAN Non-receptor tyrosine-protein kinase that plays an essential role in the selection and maturation of developing T-cells in the thymus and in the function of mature T-cells. Plays a key role in T-cell antigen receptor (TCR)-linked signal transduction pathways. Constitutively associated with the cytoplasmic portions of the CD4 and CD8 surface receptors. Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, thereby recruiting the associated LCK protein to the vicinity of the TCR/CD3 complex. LCK then phosphorylates tyrosines residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the cytoplasmic tails of the TCR-gamma chains and CD3 subunits, initiating the TCR/CD3 signaling pathway. Once stimulated, the TCR recruits the tyrosine kinase ZAP70, that becomes phosphorylated and activated by LCK. Following this, a large number of signaling molecules are recruited, ultimately leading to lymphokine production. LCK also contributes to signaling by other receptor molecules. Associates directly with the cytoplasmic tail of CD2, which leads to hyperphosphorylation and activation of LCK. Also plays a role in the IL2 receptor-linked signaling pathway that controls the T-cell proliferative response. Binding of IL2 to its receptor results in increased activity of LCK. Is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature alpha beta TCR. Phosphorylates other substrates including RUNX3, PTK2B/PYK2, the microtubule-associated protein MAPT, RHOH or TYROBP.[1] [2] [3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSrc homology-2 (SH2) domains are protein modules found within a wide variety of cytoplasmic signalling molecules that bind with high affinity to phosphotyrosyl-containing protein sequences. In order to develop SH2 inhibitors that contain phosphotyrosyl analogues resistant to cellular phosphatases, we have solved the crystal structures of the SH2 domain of p56lck in separate complexes with two high-affinity p-(phosphonomethyl)phenylalanine-containing peptides. The structures have been determined at 2.3 A and 2.25 A, and refined to crystallographic R-factors of 19.2% and 18.5%, respectively. The conformation of the SH2 domain of p56lck is essentially similar to that observed in Src and Lck complexed with a phosphotyrosine-containing peptide except in some loops and especially in the loop that connects the second and third beta-strands. This loop, which was involved in hydrogen-bond interactions with the phosphotyrosine moiety, has moved away in the phosphonopeptide complexes as a rigid body by about 7 A on two hinges leaving the tyrosine phosphate mimetic moiety accessible to the solvent. Some intramolecular hydrogen bonds with other residues of the third and fourth beta-strands stabilize an open conformation of the lid, suggesting a flap mechanism for peptide binding. The crystal structures of the SH2 domain of p56lck complexed with two phosphonopeptides suggest a gated peptide binding site.,Mikol V, Baumann G, Keller TH, Manning U, Zurini MG J Mol Biol. 1995 Feb 17;246(2):344-55. PMID:7532720[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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