title: Near-atomic resolution for one state of F-actin.
abstract: Actin functions as a helical polymer, F-actin, but attempts to build an atomic model for this filament have been hampered by the fact that the filament cannot be crystallized and by structural heterogeneity. We have used a direct electron detector, cryo-electron microscopy, and the forces imposed on actin filaments in thin films to reconstruct one state of the filament at 4.7 Å resolution, which allows for building a reliable pseudo-atomic model of F-actin. We also report a different state of the filament where actin protomers adopt a conformation observed in the crystal structure of the G-actin-profilin complex with an open ATP-binding cleft. Comparison of the two structural states provides insights into ATP-hydrolysis and filament dynamics. The atomic model provides a framework for understanding why every buried residue in actin has been under intense selective pressure.
authors.affiliation: Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507, USA. Electronic address: galkinve@evms.edu.
authors.forename: Vitold E
authors.initials: VE
authors.lastname: Galkin
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USA.
authors.forename: Albina
authors.initials: A
authors.lastname: Orlova
authors.affiliation: FEI Company, Nanoport Europe, 5651 GG Eindhoven, the Netherlands.
authors.forename: Matthijn R
authors.initials: MR
authors.lastname: Vos
authors.affiliation: Institute of Complex Systems, Forschungszentrum Jülich, 52425 Jülich, Germany; Physics Department, University of Düsseldorf, 40225 Düsseldorf, Germany.
authors.forename: Gunnar F
authors.initials: GF
authors.lastname: Schröder
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USA. Electronic address: egelman@virginia.edu.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Egelman
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D010710:Phosphates / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011817:Rabbits
chemical_list: D000199:Actins; D009711:Nucleotides; D010710:Phosphates