title: Cryo-electron microscopy structure of a yeast mitochondrial preprotein translocase.
abstract: The translocase of the outer mitochondrial membrane (TOM) complex is the main entry gate for proteins imported into mitochondria. We determined the structure of the native, unstained approximately 550-kDa core-Tom20 complex from Saccharomycescerevisiae by cryo-electron microscopy at 18-A resolution. The complex is triangular, measuring 145 A on edge, and has near-3-fold symmetry. Its bulk is made up of three globular approximately 50-A domains. Three elliptical pores on the c-face merge into one central approximately 70-A cavity with a cage-like assembly on the opposite t-face. Nitrilotriacetic acid-gold labeling indicates that three Tom22 subunits in the TOM complex are located at the perimeter of the complex near the interface of the globular domains. We assign Tom22, which controls complex assembly, to three peripheral protrusions on the c-face, while the Tom20 subunit is tentatively assigned to the central protrusion on this surface. Based on our three-dimensional map, we propose a model of transient interactions and functional dynamics of the TOM assembly.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany. Kirstin.Model@mpibp-frankfurt.mpg.de
authors.forename: Kirstin
authors.initials: K
authors.lastname: Model
authors.forename: Chris
authors.initials: C
authors.lastname: Meisinger
authors.forename: Werner
authors.initials: W
authors.lastname: Kühlbrandt
mesh_terms: D020285:Cryoelectron Microscopy; D026901:Membrane Transport Proteins / Q000648:ultrastructure; D008928:Mitochondria / Q000648:ultrastructure*; D033681:Mitochondrial Membrane Transport Proteins; D008958:Models, Molecular; D009571:Nitrilotriacetic Acid / Q000031:analogs & derivatives; D009942:Organometallic Compounds; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism / Q000648:ultrastructure*; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D009942:Organometallic Compounds; D021122:Protein Subunits; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; C489350:TOM20 protein, S cerevisiae; C090857:TOM22 protein, S cerevisiae; C088321:nickel nitrilotriacetic acid; D009571:Nitrilotriacetic Acid