title: Solution structure of the SH3 domain from Bruton's tyrosine kinase.
abstract: X-linked agammaglobulinemia (XLA) is a heritable immunodeficiency caused by mutations in the gene coding for Bruton's tyrosine kinase (Btk). Btk belongs to the Tec family of tyrosine kinases. Each member of the family contains five regions and mutations causing XLA have been isolated in all five regions. We have determined the solution structure of the Src homology 3 (SH3) domain of Btk using two- and three-dimensional nuclear magnetic resonance (NMR) spectroscopy on natural abundance and 15N-labeled protein material. The structure determination is complemented by investigation of backbone dynamics based on 15N NMR relaxation. The Btk SH3 forms a well-defined structure and shows the typical SH3 topology of two short antiparallel beta-sheets packed almost perpendicular to each other in a sandwich-like fold. The N- and C-termini are more flexible as are peptide fragments in the RT and n-Src loops. The studied Btk SH3 fragment adopts two slowly interconverting conformations with a relative concentration ratio of 7:1. The overall fold of the minor form is similar to that of the major form, as judged on the basis of observed NOE connectivities and small chemical shift differences. A tryptophan (W251) ring flip is the favored mechanism for interconversion, although other possibilities cannot be excluded. The side chain of Y223, which becomes autophosphorylated upon activation of Btk, is exposed within the potential SH3 ligand binding site. Finally, we compare the present Btk SH3 structure with other SH3 structures.
authors.affiliation: Center for Structural Biochemistry, Department of Biochemistry and Biotechnology, Royal Institute of Technology, Novum, S-141 57 Huddinge, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Hansson
authors.forename: P T
authors.initials: PT
authors.lastname: Mattsson
authors.forename: P
authors.initials: P
authors.lastname: Allard
authors.forename: P
authors.initials: P
authors.lastname: Haapaniemi
authors.forename: M
authors.initials: M
authors.lastname: Vihinen
authors.forename: C I
authors.initials: CI
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: Hard
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000361:Agammaglobulinemia / Q000201:enzymology / Q000235:genetics; D000595:Amino Acid Sequence; D008040:Genetic Linkage; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry*; D016415:Sequence Alignment; D012996:Solutions; D013329:Structure-Activity Relationship; D014960:X Chromosome; D018909:src Homology Domains
chemical_list: D012996:Solutions; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human