title: Structural features of the full-length adaptor protein GADS in solution determined using small-angle X-ray scattering.
abstract: The Grb2-related adaptor protein GADS plays a central role during the initial phases of signal transduction in T lymphocytes. GADS possesses N- and C-terminal Src homology 3 (SH3) domains flanking a central Src homology 2 (SH2) domain and a 126-residue region rich in glutamine and proline residues, presumed to be largely unstructured. The SH2 domain of GADS binds the adaptor protein LAT; the C-terminal SH3 domain pairs GADS to the adaptor protein SLP-76, whereas the function of the central region is unknown. High-resolution three-dimensional models are available for the isolated SH2 and C-terminal SH3 domains in complex with their respective binding partners, LAT and SLP-76. However, in part because of its intrinsic instability, there is no structural information for the entire GADS molecule. Here, we report the low-resolution structure of full-length GADS in solution using small-angle x-ray scattering (SAXS). Based on the SAXS data, complemented by gel filtration experiments, we show that full-length GADS is monomeric in solution and that its overall structural parameters are smaller than those expected for a protein with a long unstructured region. Ab initio and rigid body modeling of the SAXS data reveal that full-length GADS is a relatively compact molecule and that the potentially unstructured region retains a significant degree of structural order. The biological function of GADS is discussed based on its overall structure.
authors.affiliation: Istituto di Biofisica, Consiglio Nazionale delle Ricerche, 16149 Genova, Italy.
authors.forename: Oscar
authors.initials: O
authors.lastname: Moran
authors.forename: Manfred W
authors.initials: MW
authors.lastname: Roessle
authors.forename: Roy A
authors.initials: RA
authors.lastname: Mariuzza
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Dimasi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D002850:Chromatography, Gel; D011485:Protein Binding; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D053838:Scattering, Small Angle; D012996:Solutions / Q000737:chemistry; D013601:T-Lymphocytes / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C409587:GRAP2 protein, human; D011948:Receptors, Antigen, T-Cell; D012996:Solutions