title: SpoIIIE mechanism of directional translocation involves target search coupled to sequence-dependent motor stimulation.
abstract: SpoIIIE/FtsK are membrane-anchored, ATP-fuelled, directional motors responsible for chromosomal segregation in bacteria. Directionality in these motors is governed by interactions between specialized sequence-recognition modules (SpoIIIE-γ/FtsK-γ) and highly skewed chromosomal sequences (SRS/KOPS). Using a new combination of ensemble and single-molecule methods, we dissect the series of steps required for SRS localization and motor activation. First, we demonstrate that SpoIIIE/DNA association kinetics are sequence independent, with binding specificity being uniquely determined by dissociation. Next, we show by single-molecule and modelling methods that hexameric SpoIIIE binds DNA non-specifically and finds SRS by an ATP-independent target search mechanism, with ensuing oligomerization and binding of SpoIIIE-γ to SRS triggering motor stimulation. Finally, we propose a new model that provides an entirely new interpretation of previous observations for the origin of SRS/KOPS-directed translocation by SpoIIIE/FtsK.
authors.affiliation: Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université de Montpellier I & II, 34090 Montpellier, France.
authors.forename: Diego I
authors.initials: DI
authors.lastname: Cattoni
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Chara
authors.forename: Cédric
authors.initials: C
authors.lastname: Godefroy
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Margeat
authors.forename: Sonia
authors.initials: S
authors.lastname: Trigueros
authors.forename: Pierre-Emmanuel
authors.initials: PE
authors.lastname: Milhiet
authors.forename: Marcelo
authors.initials: M
authors.lastname: Nöllmann
mesh_terms: D016880:Anisotropy; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D011485:Protein Binding; D021381:Protein Transport; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C030069:spore-specific proteins, Bacillus
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