Bacterial Condensin MukBEF: Mechanism and Function of the Chromosomal Architect

When: Thursday, August 02, 2012 at 4:00 pm
Where: DA 114
Speaker: Valentin V. Rybenkov
Organization: Department of Chemistry and Biochemistry, University of Oklahoma
Sponsor: CIRCS

Across kingdoms of life, condensins play a central role in global chromosome
organization. Using a combination of biochemistry and single DNA nanomanipulations,
we explored DNA organization by the Escherichia coli condensin MukBEF. We show
that MukBEF acts as an ATP modulated macromolecular assembly that can bring distant
DNAs into a stable complex. MukBEF binds DNA in a highly cooperative, ATPstimulated
manner producing oligomeric protein clamps. These clamps are highly
resilient to applied force and can form a bridge with another DNA. The resulting activity
offers a biochemical mechanism for self-assembly of the chromosome scaffold and
suggests that MukBEF forms a network of loosely linked clamps that divides the
chromosome into a set of giant loops. Biochemical dissection of the complex indicates
that all DNA reshaping activities of MukBEF reside in its SMC (structural maintenance of
chromosome) subunit MukB, whereas MukEF plays a regulatory role and is also
responsible for focal subcellular localization of the complex. Finally, we describe a novel
family of condensins, MksBEF, which often coexists with other condensins in numerous
environmental and pathogenic bacteria.