The Bacterial Condensin MukBEF Compacts DNA into a Repetitive, Stable Structure

摘要: Condensins are conserved proteins containing SMC (structural maintenance of chromosomes) moieties that organize and compact chromosomes in an unknown mechanism essential for faithful chromosome partitioning. We show MukBEF, the condensin Escherichia coli , cooperatively compacts a single DNA molecule into filament with ordered, repetitive structure adenosine triphosphate (ATP) binding–dependent manner. When stretched to tension ∼17 piconewtons, extended series transitions broad distribution centered on 45 nanometers. A so held at lower force recondensed steps 35 nanometers or its multiples; this cycle was repeatable even absence ATP free MukBEF. Remarkably, pattern displayed by given during initial extension identical every subsequent extension. Hence, after being deformed micrometers length, each returned original without addition energy. Incubation topoisomerase I increased rate recondensation allowed extend reform almost reversibly, indicating supercoiled is trapped condensed structure. suggest new model how MukBEF organizes bacterial vivo.