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A role for the FtsQLB complex in cytokinetic ring activation revealed by an ftsL allele that accelerates division.

ABSTRACT: The cytokinetic apparatus of bacteria is initially formed by the polymerization of the tubulin-like FtsZ protein into a ring structure at midcell. This so-called Z-ring facilitates the recruitment of many additional proteins to the division site to form the mature divisome machine. Although the assembly pathway leading to divisome formation has been well characterized, the mechanisms that trigger cell constriction remain unclear. In this report, we study a 'forgotten' allele of ftsL from Escherichia coli, which encodes a conserved division gene of unknown function. We discovered that this allele promotes the premature initiation of cell division. Further analysis also revealed that the mutant bypasses the requirement for the essential division proteins ZipA, FtsK and FtsN, and partially bypasses the need for FtsA. These findings suggest that rather than serving simply as a protein scaffold within the divisome, FtsL may play a more active role in the activation of the machine. Our results support a model in which FtsL, along with its partners FtsB and FtsQ, function as part of a sensing mechanism that promotes the onset of cell wall remodeling processes needed for the initiation of cell constriction once assembly of the divisome complex is deemed complete.

SUBMITTER: Tsang MJ

PROVIDER: S-EPMC4414402 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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A role for the FtsQLB complex in cytokinetic ring activation revealed by an ftsL allele that accelerates division.

Tsang Mary-Jane MJ Bernhardt Thomas G TG

Molecular microbiology 20150124 6

The cytokinetic apparatus of bacteria is initially formed by the polymerization of the tubulin-like FtsZ protein into a ring structure at midcell. This so-called Z-ring facilitates the recruitment of many additional proteins to the division site to form the mature divisome machine. Although the assembly pathway leading to divisome formation has been well characterized, the mechanisms that trigger cell constriction remain unclear. In this report, we study a 'forgotten' allele of ftsL from Escheri ...[more]

PMID: 25496050

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Project description:BackgroundBacterial division is produced by the formation of a macromolecular complex in the middle of the cell, called the divisome, formed by more than 10 proteins. This process can be divided into two steps, in which the first is the polymerization of FtsZ to form the Z ring in the cytoplasm, and then the sequential addition of FtsA/ZipA to anchor the ring at the cytoplasmic membrane, a stage completed by FtsEX and FtsK. In the second step, the formation of the peptidoglycan synthesis machinery in the periplasm takes place, followed by cell division. The proteins involved in connecting both steps in cell division are FtsQ, FtsB and FtsL, and their interaction is a crucial and conserved event in the division of different bacteria. These components are small bitopic membrane proteins, and their specific function seems to be mainly structural. The purpose of this study was to obtain a structural model of the periplasmic part of the FtsB/FtsL/FtsQ complex, using bioinformatics tools and experimental data reported in the literature.ResultsTwo oligomeric models for the periplasmic region of the FtsB/FtsL/FtsQ E. coli complex were obtained from bioinformatics analysis. The FtsB/FtsL subcomplex was modelled as a coiled-coil based on sequence information and several stoichiometric possibilities. The crystallographic structure of FtsQ was added to this complex, through protein-protein docking. Two final structurally-stable models, one trimeric and one hexameric, were obtained. The nature of the protein-protein contacts was energetically favourable in both models and the overall structures were in agreement with the experimental evidence reported.ConclusionsThe two models obtained for the FtsB/FtsL/FtsQ complex were stable and thus compatible with the in vivo periplasmic complex structure. Although the hexameric model 2:2:2 has features that indicate that this is the most plausible structure, the ternary complex 1:1:1 cannot be discarded. Both models could be further stabilized by the binding of the other proteins of the divisome. The bioinformatics modelling of this kind of protein complex, whose function is mainly structural, provide useful information. Experimental results should confirm or reject these models and provide new data for future bioinformatics studies to refine the models.

Dataset Information

A role for the FtsQLB complex in cytokinetic ring activation revealed by an ftsL allele that accelerates division.

Publications

A role for the FtsQLB complex in cytokinetic ring activation revealed by an ftsL allele that accelerates division.

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