title: Prokaryotic origin of the actin cytoskeleton.
abstract: It was thought until recently that bacteria lack the actin or tubulin filament networks that organize eukaryotic cytoplasm. However, we show here that the bacterial MreB protein assembles into filaments with a subunit repeat similar to that of F-actin-the physiological polymer of eukaryotic actin. By elucidating the MreB crystal structure we demonstrate that MreB and actin are very similar in three dimensions. Moreover, the crystals contain protofilaments, allowing visualization of actin-like strands at atomic resolution. The structure of the MreB protofilament is in remarkably good agreement with the model for F-actin, showing that the proteins assemble in identical orientations. The actin-like properties of MreB explain the finding that MreB forms large fibrous spirals under the cell membrane of rod-shaped cells, where they are involved in cell-shape determination. Thus, prokaryotes are now known to possess homologues both of tubulin, namely FtsZ, and of actin.
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, UK. fent@mrc-lmb.cam.ac.uk
authors.forename: F
authors.initials: F
authors.lastname: van den Ent
authors.forename: L A
authors.initials: LA
authors.lastname: Amos
authors.forename: J
authors.initials: J
authors.lastname: Löwe
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D001665:Binding Sites; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D003599:Cytoskeleton / Q000737:chemistry* / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D004926:Escherichia coli; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011387:Prokaryotic Cells; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D020124:Thermotoga maritima / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; C435905:MreB1 protein, Thermotoga maritima; D009711:Nucleotides