title: Molecular cloning of a porcine gene syk that encodes a 72-kDa protein-tyrosine kinase showing high susceptibility to proteolysis.
abstract: By using antibodies raised against a portion of N terminus of 40-kDa kinase (Kobayashi, T., Nakamura, S., Taniguchi, T., and Yamamura, H. (1990) Eur. J. Biochem. 188, 535-540), not only 40-kDa protein but also 72-kDa protein were detected on immunoblot analysis of porcine spleen homogenate. In splenocytes preparation, the antibodies could immunoprecipitate protein-tyrosine kinase activity of the 72-kDa protein but not detect the 40-kDa protein even on immunoblot. After incubation of crude spleen homogenate at 37 degrees C with or without various protease inhibitors, immunoblot analysis revealed proteolytic breakdown of the 72-kDa protein to 40-kDa fragment. Next, using oligonucleotides designed according to partially sequenced information of the 40-kDa kinase as a probe, we have isolated a clone containing entire coding sequence for the 40-kDa kinase from a porcine spleen cDNA library. This clone had a 1884-base-pair-long open reading frame encoding 628-amino-acid polypeptide with a calculated molecular weight of 71,618. The deduced amino acid sequence did not contain a ligand binding or membrane spanning region but did a well-conserved protein-tyrosine kinase domain and two src homology region 2 domains. The sequences of these domains showed 30-40% identity to those of other protein-tyrosine kinases, but those of remaining parts were quite unique. From these results, we concluded that the 40-kDa kinase was generated by proteolysis from the 72-kDa holoprotein which was a new member of nonreceptor protein-tyrosine kinase so far reported. We therefore designated this gene as syk after spleen tyrosine kinase.
authors.affiliation: Department of Biochemistry, Fukui Medical School, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Taniguchi
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.forename: J
authors.initials: J
authors.lastname: Kondo
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Nakamura
authors.forename: J
authors.initials: J
authors.lastname: Suzuki
authors.forename: K
authors.initials: K
authors.lastname: Nagai
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: S
authors.initials: S
authors.lastname: Nakamura
authors.forename: H
authors.initials: H
authors.lastname: Yamamura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D003001:Cloning, Molecular; D006868:Hydrolysis; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013154:Spleen / Q000201:enzymology; D013552:Swine
chemical_list: D012333:RNA, Messenger; D011505:Protein-Tyrosine Kinases