Structural organization of the FtsLB complex of the bacterial divisome

Abstract

In Escherichia coli, FtsLB plays a central role in the initiation of cell division, possibly transducing a signal that will eventually lead to the activation of peptidoglycan remodeling at the forming septum. The molecular mechanisms by which FtsLB operates in the divisome, however, are not understood. We present a structural analysis of the FtsLB complex – performed with biophysical, computational and in vivo methods – that establishes the organization of the transmembrane region and proximal coiled coil of the complex. FRET analysis in vitro is consistent with formation of a tetramer composed of two FtsL and two FtsB subunits. We predicted subunit contacts through co‐evolutionary analysis and used them to compute a structural model of the complex. The transmembrane region of FtsLB is stabilized by hydrophobic packing and by a complex network of hydrogen bonds. The coiled coil domain likely terminates near the critical Constriction Control Domain, which might correspond to a structural transition. Presence of strongly polar amino acids within the core of the tetrameric coiled coil suggests that the coil may split into two independent FtsQ‐binding domains. The helix of FtsB is interrupted between the transmembrane and coiled coil regions by a flexible Gly‐rich linker. Conversely, the data suggest that FtsL forms an uninterrupted helix across the two regions, and that integrity of this helix is indispensable for the function of the complex. The FtsL helix is thus a candidate for acting as a potential mechanical connection to communicate conformational changes between periplasmic, membrane, and cytoplasmic regions.Support or Funding InformationThe work was supported by National Institutes of Health Grant (NIH) R01‐GM0997522 and National Science Foundation (NSF) grant CHE‐1415910 and DMS‐1661900. S.G.F.C. and G.D.V. acknowledge support by the NLM training grant 5T15LM0073.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.