Prokaryotic origin of the actin cytoskeleton

• Published in: Nature (London) 2001-09, Vol.413 (6851), p.39-44
• Main Authors: van den Ent, Fusinita, Amos, Linda A, Löwe, Jan
• Format: Article
• Language: English
• Subjects: Actins - chemistry; Actins - genetics; Actins - physiology; Actins - ultrastructure; Amino Acid Sequence; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Bacterial Proteins - ultrastructure; Bacteriology; Binding Sites; Biogenesis of cell structures, supramolecular organization; Biological and medical sciences; Cells; Cloning, Molecular; Crystallography, X-Ray; Crystals; Cytoskeletal Proteins - chemistry; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - physiology; Cytoskeletal Proteins - ultrastructure; Cytoskeleton - chemistry; Cytoskeleton - genetics; Cytoskeleton - physiology; Cytoskeleton - ultrastructure; Escherichia coli; Evolution; FtsZ protein; Fundamental and applied biological sciences. Psychology; Humanities and Social Sciences; Microbiology; Models, Molecular; Molecular biology; Molecular Sequence Data; MreB protein; multidisciplinary; Nucleotides - metabolism; Physiology; Polymerase Chain Reaction; Polymers; Prokaryotic Cells; Protein Conformation; Science; Sequence Homology, Amino Acid; Structure-Activity Relationship; Thermotoga maritima - chemistry; Thermotoga maritima - ultrastructure
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/35092500

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.