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SpoIIIE mechanism of directional translocation involves target search coupled to sequence‐dependent motor stimulation
Author(s) -
Cattoni Diego I,
Chara Osvaldo,
Godefroy Cédric,
Margeat Emmanuel,
Trigueros Sonia,
Milhiet PierreEmmanuel,
Nöllmann Marcelo
Publication year - 2013
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/embor.2013.39
Subject(s) - chromosomal translocation , dna , directionality , biology , molecular motor , sequence (biology) , mechanism (biology) , biophysics , computational biology , microbiology and biotechnology , chemistry , genetics , gene , physics , quantum mechanics
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.