title: F-actin-like filaments formed by plasmid segregation protein ParM.
abstract: It was the general belief that DNA partitioning in prokaryotes is independent of a cytoskeletal structure, which in eukaryotic cells is indispensable for DNA segregation. Recently, however, immunofluorescence microscopy revealed highly dynamic, filamentous structures along the longitudinal axis of Escherichia coli formed by ParM, a plasmid-encoded protein required for accurate segregation of low-copy-number plasmid R1. We show here that ParM polymerizes into double helical protofilaments with a longitudinal repeat similar to filamentous actin (F-actin) and MreB filaments that maintain the cell shape of non-spherical bacteria. The crystal structure of ParM with and without ADP demonstrates that it is a member of the actin family of proteins and shows a domain movement of 25 degrees upon nucleotide binding. Furthermore, the crystal structure of ParM reveals major differences in the protofilament interface compared with F-actin, despite the similar arrangement of the subunits within the filaments. Thus, there is now evidence for cytoskeletal structures, formed by actin-like filaments that are involved in plasmid partitioning in E.coli.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Fusinita
authors.initials: F
authors.lastname: van den Ent
authors.forename: Jakob
authors.initials: J
authors.lastname: Møller-Jensen
authors.forename: Linda A
authors.initials: LA
authors.lastname: Amos
authors.forename: Kenn
authors.initials: K
authors.lastname: Gerdes
authors.forename: Jan
authors.initials: J
authors.lastname: Löwe
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology*; D018360:Crystallography, X-Ray; D003599:Cytoskeleton / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D008854:Microscopy, Electron; D008958:Models, Molecular; D010957:Plasmids / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D000199:Actins; D029968:Escherichia coli Proteins; C471255:ParM protein, E coli; C078473:MreB protein, E coli; D004247:DNA