Title

Molecular mechanism by which the nucleoid occlusion factor, SlmA, keeps cytokinesis in check.

Publication Date

1-5-2011

Journal

EMBO J. 2011 January 5; 30(1): 154–164.

Abstract

In Escherichia coli, cytokinesis is orchestrated by FtsZ, which forms a Z-ring to drive septation. Spatial and temporal control of Z-ring formation is achieved by the Min and nucleoid occlusion (NO) systems. Unlike the well-studied Min system, less is known about the anti-DNA guillotining NO process. Here, we describe studies addressing the molecular mechanism of SlmA (synthetic lethal with a defective Min system)-mediated NO. SlmA contains a TetR-like DNA-binding fold, and chromatin immunoprecipitation analyses show that SlmA-binding sites are dispersed on the chromosome except the Ter region, which segregates immediately before septation. SlmA binds DNA and FtsZ simultaneously, and the SlmA-FtsZ structure reveals that two FtsZ molecules sandwich a SlmA dimer. In this complex, FtsZ can still bind GTP and form protofilaments, but the separated protofilaments are forced into an anti-parallel arrangement. This suggests that SlmA may alter FtsZ polymer assembly. Indeed, electron microscopy data, showing that SlmA-DNA disrupts the formation of normal FtsZ polymers and induces distinct spiral structures, supports this. Thus, the combined data reveal how SlmA derails Z-ring formation at the correct place and time to effect NO.

Keywords

Bacterial Proteins, Base Sequence, Binding Sites, Carrier Proteins, Chromosomes, Bacterial, Crystallography, X-Ray, Cytokinesis, Cytoskeletal Proteins, DNA, Bacterial, Escherichia coli, Escherichia coli Proteins, Models, Molecular, Protein Binding, Protein Conformation, Protein Multimerization, Scattering, Small Angle, X-Ray Diffraction