title: Purification and spectroscopic characterization of the human protein tyrosine kinase-6 SH3 domain.
abstract: The human protein tyrosine kinase-6 (PTK6) polypeptide that is deduced from the cDNA sequence contains a Src homology (SH) 3 domain, SH2 domain, and catalytic domain of tyrosine kinase. We initiated biochemical and NMR characterization of PTK6 SH3 domain in order to correlate the structural role of the PTK6 using circular dichroism and heteronuclear NMR techniques. The circular dichroism data suggested that the secondary structural elements of the SH3 domain are mainly composed of beta-sheet conformations. It is most stable when the pH is neutral based on the pH titration data. In addition, a number of cross peaks at the low-field area of the proton chemical shift of the NMR spectra indicated that the PTK6 SH3 domain retains a unique and folded conformation at the neutral pH condition. For other pH conditions, the SH3 domain became unstable and aggregated during NMR measurements, indicating that the structural stability is very sensitive to pH environments. Both the NMR and circular dichroism data indicate that the PTK6 SH3 domain experiences a conformational instability, even in an aqueous solution.
authors.affiliation: Department of Biochemistry and Protein Network Research Center, College of Science, Yonsei University, Seoul 120-749, Korea.
authors.forename: Bon-Kyung
authors.initials: BK
authors.lastname: Koo
authors.forename: Min-Hyung
authors.initials: MH
authors.lastname: Kim
authors.forename: Seung-Taek
authors.initials: ST
authors.lastname: Lee
authors.forename: Weontae
authors.initials: W
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains
chemical_list: D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D011505:Protein-Tyrosine Kinases