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J Biol Chem. 2018 Feb 2;293(5):1623-1641. doi: 10.1074/jbc.RA117.000426. Epub 2017 Dec 12.

The FtsLB subcomplex of the bacterial divisome is a tetramer with an uninterrupted FtsL helix linking the transmembrane and periplasmic regions.

Author information

1
From the Department of Biochemistry.
2
the Integrated Program in Biochemistry.
3
the Biophysics Graduate Program, and.
4
the Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242.
5
the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 and.
6
From the Department of Biochemistry, senes@wisc.edu.

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. Here, 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 probably terminates near the critical constriction control domain, which might correspond to a structural transition. The 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 the 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.

KEYWORDS:

Escherichia coli (E. coli); bacteria; bacterial genetics; bioinformatics; cell division; co-evolution; computational biology; divisome; fluorescence resonance energy transfer (FRET); membrane protein; molecular dynamics; molecular modeling

PMID:
29233891
PMCID:
PMC5798294
[Available on 2019-02-02]
DOI:
10.1074/jbc.RA117.000426

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