title: Solution behavior and crystallization of cytochrome bc₁ in the presence of amphipols.
abstract: Detergents classically are used to keep membrane proteins soluble in aqueous solutions, but they tend to destabilize them. This problem can be largely alleviated thanks to the use of amphipols (APols), small amphipathic polymers designed to substitute for detergents. APols adsorb at the surface of the transmembrane region of membrane proteins, keeping them water-soluble while stabilizing them bio-chemically. Membrane protein/APol complexes have proven, however, difficult to crystallize. In this study, the composition and solution properties of complexes formed between mitochondrial cytochrome bc1 and A8-35, the most extensively used APol to date, have been studied by means of size exclusion chromatography, sucrose gradient sedimentation, and small-angle neutron scattering. Stable, monodisperse preparations of bc1/A8-35 complexes can be obtained, which, depending on the medium, undergo either repulsive or attractive interactions. Under crystallization conditions, diffracting three-dimensional crystals of A8-35-stabilized cytochrome bc1 formed, but only in the concomitant presence of APol and detergent.
authors.affiliation: UMR 7099, Centre National de la Recherche Scientifique/Université Paris-7, Institut de Biologie Physico-Chimique, FRC 550, 13, rue Pierre-et-Marie-Curie, 75005, Paris, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Charvolin
authors.forename: Martin
authors.initials: M
authors.lastname: Picard
authors.forename: Li-Shar
authors.initials: LS
authors.lastname: Huang
authors.forename: Edward A
authors.initials: EA
authors.lastname: Berry
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Popot
mesh_terms: D003460:Crystallization / Q000379:methods*; D003902:Detergents / Q000737:chemistry*; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000648:ultrastructure*; D057927:Hydrophobic and Hydrophilic Interactions; D011108:Polymers / Q000737:chemistry*; D011437:Propylamines / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D012995:Solubility; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D003902:Detergents; D011108:Polymers; D011437:Propylamines; D012996:Solutions; D013501:Surface-Active Agents; C499017:amphipol A8-35; D014867:Water; D014450:Electron Transport Complex III