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.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • B-Lymphocytes / enzymology*
  • B-Lymphocytes / immunology
  • Base Sequence
  • Cell Line
  • Chromosome Mapping
  • Chromosomes, Human, Pair 9*
  • Cloning, Molecular / methods
  • Conserved Sequence
  • DNA, Complementary / analysis
  • Enzyme Precursors / biosynthesis*
  • Enzyme Precursors / genetics
  • Enzyme Precursors / isolation & purification*
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Molecular Sequence Data
  • Phosphorylation
  • Protein-Tyrosine Kinases / biosynthesis*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / isolation & purification*
  • RNA, Messenger / analysis
  • RNA, Messenger / biosynthesis
  • Receptors, Antigen, B-Cell / isolation & purification*
  • Receptors, Antigen, B-Cell / metabolism
  • Restriction Mapping
  • Sequence Homology, Amino Acid
  • Spleen / enzymology
  • Swine
  • Syk Kinase
  • T-Lymphocytes / immunology
  • Transfection


  • DNA, Complementary
  • Enzyme Precursors
  • Intracellular Signaling Peptides and Proteins
  • RNA, Messenger
  • Receptors, Antigen, B-Cell
  • Protein-Tyrosine Kinases
  • SYK protein, human
  • Syk Kinase
  • Syk protein, mouse

Associated data

  • GENBANK/L28824