title: Structural basis of the auto-inhibition mechanism of nonreceptor tyrosine kinase PTK6.
abstract: Protein tyrosine kinase 6 (PTK6) is composed of SH3, SH2, and Kinase domains, with a linker region (Linker) between the SH2 and Kinase domains. Here, we report the structural basis of the SH3-Linker interaction that results in auto-inhibition of PTK6. The solution structures of the SH3 domain and SH3/Linker complex were determined by NMR spectroscopy. The structure of the SH3 domain forms a conventional beta-barrel with two beta-sheets comprised of five beta-strands. However, the molecular topology and charge distribution of PTK6-SH3 slightly differs from that of the other SH3 domains. The structure of the N-terminal Linker within the complex showed that the proline-rich region (P175-P187) of the Linker forms a compact hairpin structure through hydrophobic interactions. The structure of the SH3/Linker complex revealed intra-molecular interaction between the amino acid pairs R22/E190, W44/W184, N65/P177, and Y66/P179. Mutations in PTK6 at R22, W44, N65, and Y66 residues in the SH3 domain increased catalytic activity compared with wild-type protein, implying that specific interactions between hydrophobic residues in the proline-rich linker region and hydrophobic residues in the SH3 domain are mainly responsible for down-regulating the catalytic activity of PTK6.
authors.affiliation: Department of Biochemistry, College of Life Science & Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea.
authors.forename: Sunggeon
authors.initials: S
authors.lastname: Ko
authors.forename: Kyo-Eun
authors.initials: KE
authors.lastname: Ahn
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Lee
authors.forename: Hee-Chul
authors.initials: HC
authors.lastname: Ahn
authors.forename: Weontae
authors.initials: W
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D009154:Mutation; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D018909:src Homology Domains / Q000235:genetics
chemical_list: D009363:Neoplasm Proteins; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human