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| Subject Categories: Structural Biology | Cell & Tissue Architecture |
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| The EMBO Journal
(2002) 21, 6935–6943, doi: 10.1093/emboj/cdf672 |
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| F-actin-like filaments formed by plasmid segregation protein ParM |
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| Fusinita van den Ent1, 3, Jakob Møller-Jensen2, 3, Linda A. Amos1, Kenn Gerdes2 and Jan Löwe1 |
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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 To whom correspondence should be addressed Jan Löwe, jyl@mrc-lmb.cam.ac.uk Received 20 August 2002; Revised 4 October 2002; Accepted 22 October 2002. |
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| Abstract |
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| 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. |
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| Keywords: DNA partitioning, F-actin, MreB, ParM |
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