Article

  • The EMBO Journal (2002) 21, 6935 - 6943
  • doi:10.1093/emboj/cdf672

F-actin-like filaments formed by plasmid segregation protein ParM

Fusinita van den Ent1,3, Jakob Møller-Jensen2,3, Linda A. Amos1, Kenn Gerdes2 and Jan Löwe1

  1. MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
  2. Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
  3. F.van den Ent and J.Møller-Jensen contributed equally to this work

Correspondence to:

Jan Löwe, E-mail: jyl@mrc-lmb.cam.ac.uk

Received 20 August 2002; Accepted 22 October 2002; Revised 4 October 2002


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° 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.

  • Keywords:

    • DNA partitioning,
    • F-actin,
    • MreB,
    • ParM