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The metabolic enzyme CTP synthase forms cytoskeletal filaments

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Abstract

Filament-forming cytoskeletal proteins are essential for the structure and organization of all cells. Bacterial homologues of the major eukaryotic cytoskeletal families have now been discovered, but studies suggest that yet more remain to be identified. We demonstrate that the metabolic enzyme CTP synthase (CtpS) forms filaments in Caulobacter crescentus. CtpS is bifunctional, as the filaments it forms regulate the curvature of C. crescentus cells independently of its catalytic function. The morphogenic role of CtpS requires its functional interaction with the intermediate filament, crescentin (CreS). Interestingly, the Escherichia coli CtpS homologue also forms filaments both in vivo and in vitro, suggesting that CtpS polymerization may be widely conserved. E. coli CtpS can replace the enzymatic and morphogenic functions of C. crescentus CtpS, indicating that C. crescentus has adapted a conserved filament-forming protein for a secondary role. These results implicate CtpS as a novel bifunctional member of the bacterial cytoskeleton and suggest that localization and polymerization may be important properties of metabolic enzymes.

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Figure 1: mCherry–CtpS is dynamic and co-localizes with linear filamentous structures along the inner curvature of C. crescentus cells.
Figure 2: CtpS forms filaments in C. crescentus.
Figure 3: CtpS regulates C. crescentus cell shape independently of its enzymatic activity.
Figure 4: CtpS regulates cell shape through an interaction with CreS.
Figure 5: The E. coli CtpS homologue forms filaments both in vivo and in vitro.

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Acknowledgements

We are grateful to B. Bassler, C. Murphy, E. Klein and K. Cowles for critical reading of the manuscript. We thank M. Cabeen, C. Jacobs-Wagner, J. Williamson, Alison Michaelis and other members of the Gitai lab for reagents and discussions. J.N.W. is supported by a postdoctoral fellowship from the National Institute of Allergy and Infectious Diseases (grant 1F32AI073043–01A1). A.B. and G.J.J. were supported in part by the National Institutes of Health (NIH) grant R01 AI067548, the Howard Hughes Medical Institute, and a gift to Caltech from the Gordon and Betty Moore Foundation. Z.G. is supported by funding from the U.S. Department of Energy Office of Science (Biological and Environmental Research; grant DE-FG02-05ER64136), NIH grant 1DP2OD004389-01, the Human Frontiers Science Program and the Beckman Foundation.

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M.J.I. performed all experiments except for the ECT and fLM-ECT experiments, which were performed by A.B. J.N.W. performed the initial screen that identified CtpS as a linearly localized protein. Experiments were conceived by M.J.I., A.B., G.J.J. and Z.G., and the manuscript was written by M.J.I. and Z.G. with significant input from A.B. and G.J.J.

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Correspondence to Zemer Gitai.

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Ingerson-Mahar, M., Briegel, A., Werner, J. et al. The metabolic enzyme CTP synthase forms cytoskeletal filaments. Nat Cell Biol 12, 739–746 (2010). https://doi.org/10.1038/ncb2087

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