The SMC complex, MukBEF, organizes theEscherichia colichromosome by forming an axial core

Abstract

AbstractStructural Maintenance of Chromosomes (SMC) complexes organize and individualize chromosomes ubiquitously, thereby contributing to their faithful segregation. Here we explore howEscherichia colichromosome organization emerges from the action of the SMC complex MukBEF, using quantitative imaging in cells with increased MukBEF occupancy on the chromosome. We demonstrate that theE. colichromosome is organized as series of loops around a thin axial MukBEF core whose length is ~1100 times shorter than the chromosomal DNA. The core is linear (1 μm), or circular (1.5 μm) in the absence of MatP, which displaces MukBEF from the 800 kbp replication termination region (ter). Our findings illustrate how MukBEF compacts the chromosome lengthwise and demonstrate how displacement of MukBEF fromterpromotes MukBEF enrichment with the replication origin.