SpoIIIE mechanism of directional translocation involves target search coupled to sequence-dependent motor stimulation

Journal article

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. © 2013 European Molecular Biology Organizatio.

Authors: Cattoni, D; Chara, O; Godefroy, C; Margeat, E; Trigueros, S

• Journal: EMBO Reports
• Volume: 14
• Issue: 5
• Pages: 473-479
• Publication date: 2013-05-01
• DOI: 10.1038/embor.2013.39
• EISSN: 1469-3178
• ISSN: 1469-221X
• Language: English
• Keywords: sequence-specific regulation; single molecule; translocation directionality; DNA segregation; molecular motors