title: Reconstitution of a prokaryotic minus end-tracking system using TubRC centromeric complexes and tubulin-like protein TubZ filaments.
abstract: Segregation of DNA is a fundamental process during cell division. The mechanism of prokaryotic DNA segregation is largely unknown, but several low-copy-number plasmids encode cytomotive filament systems of the actin type and tubulin type important for plasmid inheritance. Of these cytomotive filaments, only actin-like systems are mechanistically well characterized. In contrast, the mechanism by which filaments of tubulin-like TubZ protein mediate DNA motility is unknown. To understand polymer-driven DNA transport, we reconstituted the filaments of TubZ protein (TubZ filaments) from Bacillus thuringiensis pBtoxis plasmid with their centromeric TubRC complexes containing adaptor protein TubR and tubC DNA. TubZ alone assembled into polar filaments, which annealed laterally and treadmilled. Using single-molecule imaging, we show that TubRC complexes were not pushed by filament polymerization; instead, they processively tracked shrinking, depolymerizing minus ends. Additionally, the TubRC complex nucleated TubZ filaments and allowed for treadmilling. Overall, our results indicate a pulling mechanism for DNA transport by the TubZRC system. The discovered minus end-tracking property of the TubRC complex expands the mechanistic diversity of the prokaryotic cytoskeleton.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Gero
authors.initials: G
authors.lastname: Fink
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom jyl@mrc-lmb.cam.ac.uk.
authors.forename: Jan
authors.initials: J
authors.lastname: Löwe
mesh_terms: D001413:Bacillus thuringiensis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002503:Centromere / Q000235:genetics / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D009154:Mutation; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D058105:Polymerization; D011485:Protein Binding; D017433:Protein Structure, Secondary; D014404:Tubulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D004269:DNA, Bacterial; C071525:FtsZ protein, Bacteria; D014404:Tubulin
keywords: DNA segregation; cytoskeleton; tubulin homologue
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