Structure
Volume 27, Issue 7, 2 July 2019, Pages 1082-1093.e5
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Article
Structure and Assembly of the Enterohemorrhagic Escherichia coli Type 4 Pilus

https://doi.org/10.1016/j.str.2019.03.021Get rights and content
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Highlights

  • EHEC Type 4a pili are the prototype of competence co-regulated enterobacterial pili

  • Combined NMR and cryo-EM analysis provided the structure of EHEC type 4 pili

  • Major pilin displays a long, melted N-terminal segment in highly flexible EHEC pili

  • Electrostatic contacts between pilins and assembly factors drive pilus assembly

Summary

Bacterial type 4a pili are dynamic surface filaments that promote bacterial adherence, motility, and macromolecular transport. Their genes are highly conserved among enterobacteria and their expression in enterohemorrhagic Escherichia coli (EHEC) promotes adhesion to intestinal epithelia and pro-inflammatory signaling. To define the molecular basis of EHEC pilus assembly, we determined the structure of the periplasmic domain of its major subunit PpdD (PpdDp), a prototype of an enterobacterial pilin subfamily containing two disulfide bonds. The structure of PpdDp, determined by NMR, was then docked into the density envelope of purified EHEC pili obtained by cryoelectron microscopy (cryo-EM). Cryo-EM reconstruction of EHEC pili at ∼8 Å resolution revealed extremely high pilus flexibility correlating with a large extended region of the pilin stem. Systematic mutagenesis combined with functional and interaction analyses identified charged residues essential for pilus assembly. Structural information on exposed regions and interfaces between EHEC pilins is relevant for vaccine and drug discovery.

Keywords

type 4 pili
Escherichia coli
EHEC
NMR
cryo-EM
pilin structure
pilus assembly
molecular modeling
hemorrhagic coli pilus (HCP)
type II secretion system

Cited by (0)

6

These authors contributed equally

7

Present address: Núcleo Multidisciplinar de Pesquisa em Biologia - NUMPEX-BIO, Universidade Federal do Rio de Janeiro, Estrada de Xerém, RJ, Brazil

8

Lead Contact