title: Refinement of multidomain protein structures by combination of solution small-angle X-ray scattering and NMR data.
abstract: Determination of the 3D structures of multidomain proteins by solution NMR methods presents a number of unique challenges related to their larger molecular size and the usual scarcity of constraints at the interdomain interface, often resulting in a decrease in structural accuracy. In this respect, experimental information from small-angle scattering of X-ray radiation in solution (SAXS) presents a suitable complement to the NMR data, as it provides an independent constraint on the overall molecular shape. A computational procedure is described that allows incorporation of such SAXS data into the mainstream high-resolution macromolecular structure refinement. The method is illustrated for a two-domain 177-amino-acid protein, gammaS crystallin, using an experimental SAXS data set fitted at resolutions from approximately 200 A to approximately 30 A. Inclusion of these data during structure refinement decreases the backbone coordinate root-mean-square difference between the derived model and the high-resolution crystal structure of a 54% homologous gammaB crystallin from 1.96 +/- 0.07 A to 1.31 +/- 0.04 A. Combining SAXS data with NMR restraints can be accomplished at a moderate computational expense and is expected to become useful for multidomain proteins, multimeric assemblies, and tight macromolecular complexes.
authors.affiliation: Laboratory of Chemical Physics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0520, USA. grishaev@speck.niddk.nih.gov
authors.forename: Alexander
authors.initials: A
authors.lastname: Grishaev
authors.forename: Justin
authors.initials: J
authors.lastname: Wu
authors.forename: Jill
authors.initials: J
authors.lastname: Trewhella
authors.forename: Ad
authors.initials: A
authors.lastname: Bax
mesh_terms: D019295:Computational Biology; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D011506:Proteins