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Published December 2, 2008 | Published + Supplemental Material
Journal Article Open

Molecular organization of Gram-negative peptidoglycan

Abstract

The stress-bearing component of the bacterial cell wall -— a multi-gigadalton bag-like molecule called the sacculus -— is synthesized from peptidoglycan. Whereas the chemical composition and the 3-dimensional structure of the peptidoglycan subunit (in at least one conformation) are known, the architecture of the assembled sacculus is not. Four decades' worth of biochemical and electron microscopy experiments have resulted in two leading 3-D peptidoglycan models: "Layered" and "Scaffold", in which the glycan strands are parallel and perpendicular to the cell surface, respectively. Here we resolved the basic architecture of purified, frozen-hydrated sacculi through electron cryotomography. In the Gram-negative sacculus, a single layer of glycans lie parallel to the cell surface, roughly perpendicular to the long axis of the cell, encircling the cell in a disorganized hoop-like fashion.

Additional Information

© 2008 by the National Academy of Sciences. Edited by M. J. Osborn, University of Connecticut Health Center, Farmington, CT, and approved October 9, 2008 (received for review August 14, 2008). Published online before print November 24, 2008, doi:10.1073/pnas.0808035105 We thank Drs. W. F. Tivol for help with EM; H. Tsuruta and M. Hammel for help at beamlines SSRL 4-2 and ALS 12.3.1, respectively; A. Briegel, D.P. Dias, and Z. Li for sharing data; J. Skerker, K.C. Huang, N. Wingreen, and P. Leong for discussions; and Mr. Everett Kane (SuperSoft Design, New York, NY) for Fig. 1C. This work was supported in part by National Institutes of Health Grants R01 AI067548 and P50 GM082545 to G.J.J., a Searle Scholar Award to G.J.J., the Beckman Institute at Caltech, and gifts to Caltech from the Gordon and Betty Moore Foundation and the Agouron Institute. L.G. is a Damon Runyon Fellow supported by a fellowship from the Damon Runyon Cancer Research Foundation (DRG-1940-07). Author contributions: L.G. and G.J.J. designed research; L.G. and S.C. performed research; L.G., S.C., and G.J.J. analyzed data; and L.G. and G.J.J. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/cgi/content/full/0808035105/DCSupplemental.

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Created:
August 22, 2023
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October 17, 2023