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Cell. 2019 Dec 21. pii: S0092-8674(19)31332-7. doi: 10.1016/j.cell.2019.12.006. [Epub ahead of print]

InSitu Structure of an Intact Lipopolysaccharide-Bound Bacterial Surface Layer.

Author information

1
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, United Kingdom.
2
Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3TA, United Kingdom.
3
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
4
Structural Studies Division, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
5
Department of Biology, Indiana University, Bloomington, IN 47405, USA; Département de microbiologie, infectiologie et immunologie, Université de Montréal, C.P. 6128, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada.
6
Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
7
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, United Kingdom. Electronic address: tanmay.bharat@path.ox.ac.uk.

Abstract

Most bacterial and all archaeal cells are encapsulated by a paracrystalline, protective, and cell-shape-determining proteinaceous surface layer (S-layer). On Gram-negative bacteria, S-layers are anchored to cells via lipopolysaccharide. Here, we report an electron cryomicroscopy structure of the Caulobacter crescentus S-layer bound to the O-antigen of lipopolysaccharide. Using native mass spectrometry and molecular dynamics simulations, we deduce the length of the O-antigen on cells and show how lipopolysaccharide binding and S-layer assembly is regulated by calcium. Finally, we present a near-atomic resolution in situ structure of the complete S-layer using cellular electron cryotomography, showing S-layer arrangement at the tip of the O-antigen. A complete atomic structure of the S-layer shows the power of cellular tomography for in situ structural biology and sheds light on a very abundant class of self-assembling molecules with important roles in prokaryotic physiology with marked potential for synthetic biology and surface-display applications.

KEYWORDS:

LPS; S-layer; bacteria; cryo-EM; cryo-ET; in situ structural biology; lipopolysaccharide; sub-tomogram averaging; surface layer; tomography

PMID:
31883796
DOI:
10.1016/j.cell.2019.12.006
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