title: Organic solvents order the dynamic switch II in Ras crystals.
abstract: Room temperature crystal structures of crosslinked H-Ras bound to GMPPNP were solved in 50% 2,2,2-trifluoroethanol, 60% 1,6-hexanediol, and 50% isopropanol. The disordered switch II region of Ras is ordered in the presence of 2,2,2-trifluoroethanol or 1,6-hexanediol. The overall backbone conformation of switch II in these organic solvents is the same as in the Ras-GMPPNP complexes with RalGDS, PI(3) kinase, and RasGAP, indicating a biologically relevant form. Key polar interactions that stabilize the ordered switch are enhanced in the presence of hydrophobic cosolvents. These results suggest that hydrophobic solvents can be used in general to order short biologically relevant segments of disordered regions in protein crystals by favoring H-bonding interactions between atoms that are highly solvated and mobile in aqueous solution.
authors.affiliation: Department of Molecular and Structural Biochemistry, North Carolina State University, 128 Polk Hall, Raleigh, NC 27695, USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Buhrman
authors.forename: Vesna
authors.initials: V
authors.lastname: de Serrano
authors.forename: Carla
authors.initials: C
authors.lastname: Mattos
mesh_terms: D003460:Crystallization; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D018631:ras Proteins / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D012997:Solvents; D006160:Guanosine Triphosphate; D018631:ras Proteins