Molecular cloning of human Syk. A B cell protein-tyrosine kinase associated with the surface immunoglobulin M-B cell receptor complex.
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Law CL, Sidorenko SP, Chandran KA, Draves KE, Chan AC, Weiss A, Edelhoff S, Disteche CM, Clark EA
Molecular cloning of human Syk. A B cell protein-tyrosine kinase associated with the surface immunoglobulin M-B cell receptor complex.
J Biol Chem. 1994 Apr 22;269(16):12310-9.
- PubMed ID
- 8163536 [ View in PubMed]
- Abstract
B cell antigen receptors are multicomponent complexes consisting of the surface immunoglobulin and accessory molecules with associating protein-tyrosine kinases. A spleen tyrosine kinase, Syk, in porcine B cells and a 72-kDa protein-tyrosine kinase, PTK72, in murine B cells associate with the B cell antigen receptor. Herein, we report the isolation of a full-length cDNA encoding the human homologue of Syk. This cDNA predicted a polypeptide consisting of two NH2-terminal SH2 domains and a COOH-terminal tyrosine kinase domain. Syk is highly conserved between human and swine and is homologous to the T cell-associated protein-tyrosine kinase ZAP-70. Both Syk mRNA and protein were detected in cells derived from multiple hematopoietic lineages. Within the B cell compartment, Syk was expressed from pro-B cells to plasma cells. In vitro kinase assays conducted on the human Syk protein isolated from B cells revealed the presence of autophosphorylation activity on Syk tyrosine residues. Tyrosine phosphorylation of Syk associating with the B cell receptor complex in human was augmented rapidly after surface immunoglobulin cross-linking. The human SYK locus was mapped to chromosome 9 at band q22.