title: Structural characterization of flexible proteins using small-angle X-ray scattering.
abstract: Structural analysis of flexible macromolecular systems such as intrinsically disordered or multidomain proteins with flexible linkers is a difficult task as high-resolution techniques are barely applicable. A new approach, ensemble optimization method (EOM), is proposed to quantitatively characterize flexible proteins in solution using small-angle X-ray scattering (SAXS). The flexibility is taken into account by allowing for the coexistence of different conformations of the protein contributing to the experimental scattering pattern. These conformers are selected using a genetic algorithm from a pool containing a large number of randomly generated models covering the protein configurational space. Quantitative criteria are developed to analyze the EOM selected models and to determine the optimum number of conformers in the ensemble. Simultaneous fitting of multiple scattering patterns from deletion mutants, if available, provides yet more detailed local information about the structure. The efficiency of EOM is demonstrated in model and practical examples on completely or partially unfolded proteins and on multidomain proteins interconnected by linkers. In the latter case, EOM is able to distinguish between rigid and flexible proteins and to directly assess the interdomain contacts.
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, 22603 Hamburg, Germany. pbernado@pcb.ub.es
authors.forename: Pau
authors.initials: P
authors.lastname: Bernadó
authors.forename: Efstratios
authors.initials: E
authors.lastname: Mylonas
authors.forename: Maxim V
authors.initials: MV
authors.lastname: Petoukhov
authors.forename: Martin
authors.initials: M
authors.lastname: Blackledge
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
mesh_terms: D000465:Algorithms; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011505:Protein-Tyrosine Kinases / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D011506:Proteins; D011505:Protein-Tyrosine Kinases; D009113:Muramidase