Bacterial FtsZ protein forms phase-separated condensates with its nucleoid-associated inhibitor SlmA

EMBO Rep. 2019 Jan;20(1):e45946. doi: 10.15252/embr.201845946. Epub 2018 Dec 6.

Abstract

Macromolecular condensation resulting from biologically regulated liquid-liquid phase separation is emerging as a mechanism to organize intracellular space in eukaryotes, with broad implications for cell physiology and pathology. Despite their small size, bacterial cells are also organized by proteins such as FtsZ, a tubulin homolog that assembles into a ring structure precisely at the cell midpoint and is required for cytokinesis. Here, we demonstrate that FtsZ can form crowding-induced condensates, reminiscent of those observed for eukaryotic proteins. Formation of these FtsZ-rich droplets occurs when FtsZ is bound to SlmA, a spatial regulator of FtsZ that antagonizes polymerization, while also binding to specific sites on chromosomal DNA. The resulting condensates are dynamic, allowing FtsZ to undergo GTP-driven assembly to form protein fibers. They are sensitive to compartmentalization and to the presence of a membrane boundary in cell mimetic systems. This is a novel example of a bacterial nucleoprotein complex exhibiting condensation into liquid droplets, suggesting that phase separation may also play a functional role in the spatiotemporal organization of essential bacterial processes.

Keywords: bacterial division; biomolecular condensation; droplet microfluidics; macromolecular crowding; phase separation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Proteins / genetics*
  • Binding Sites
  • Carrier Proteins / genetics*
  • Cytokinesis / genetics*
  • Cytoskeletal Proteins / genetics*
  • DNA, Bacterial / genetics*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / genetics*
  • Liquid-Liquid Extraction
  • Protein Binding
  • Protein Multimerization

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • Cytoskeletal Proteins
  • DNA, Bacterial
  • Escherichia coli Proteins
  • FtsZ protein, Bacteria
  • SlmA protein, E coli