title: Activation loop dynamics determine the different catalytic efficiencies of B cell- and T cell-specific tec kinases.
abstract: Itk (interleukin-2-inducible T cell kinase) and Btk (Bruton's tyrosine kinase) are nonreceptor tyrosine kinases of the Tec family that signal downstream of the T cell receptor (TCR) and B cell receptor (BCR), respectively. Despite their high sequence similarity and related signaling roles, Btk is a substantially more active kinase than Itk. We showed that substitution of 6 of the 619 amino acid residues of Itk with the corresponding residues of Btk (and vice versa) was sufficient to completely switch the activities of Itk and Btk. The substitutions responsible for the swap in activity are all localized to the activation segment of the kinase domain. Nuclear magnetic resonance and hydrogen-deuterium exchange mass spectrometry analyses revealed that Itk and Btk had distinct protein dynamics in this region, which could explain the differences in catalytic efficiency between these kinases. Introducing Itk with enhanced activity into T cells led to enhanced and prolonged TCR signaling compared to that in cells with wild-type Itk. These findings imply that evolutionary pressures have led to Tec kinases having distinct enzymatic properties, depending on the cellular context. We suggest that the weaker catalytic activities of T cell-specific kinases serve to regulate cellular activation and prevent aberrant immune responses.
authors: Roy J Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
authors: Raji E
authors: RE
authors: Joseph
authors: Iivari
authors: I
authors: Kleino
authors: Thomas E
authors: TE
authors: Wales
authors: Qian
authors: Q
authors: Xie
authors: D Bruce
authors: DB
authors: Fulton
authors: John R
authors: JR
authors: Engen
authors: Leslie J
authors: LJ
authors: Berg
authors: Amy H
authors: AH
authors: Andreotti
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D055162:Biocatalysis; D015153:Blotting, Western; D041961:Deuterium Exchange Measurement; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D061987:Sf9 Cells; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625951:Btk protein, mouse; C080813:emt protein-tyrosine kinase
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