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J Biol Chem. 2015 Oct 30;290(44):26856-65. doi: 10.1074/jbc.M115.683334. Epub 2015 Sep 10.

Structural and functional studies of the Pseudomonas aeruginosa minor pilin, PilE.

Author information

1
From the Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario L8S 4K1 and.
2
the Department of Biochemistry, Western University, London, Ontario N6A 3K7, Canada.
3
From the Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario L8S 4K1 and burrowl@mcmaster.ca.

Abstract

Many bacterial pathogens, including Pseudomonas aeruginosa, use type IVa pili (T4aP) for attachment and twitching motility. T4aP are composed primarily of major pilin subunits, which are repeatedly assembled and disassembled to mediate function. A group of pilin-like proteins, the minor pilins FimU and PilVWXE, prime pilus assembly and are incorporated into the pilus. We showed previously that minor pilin PilE depends on the putative priming subcomplex PilVWX and the non-pilin protein PilY1 for incorporation into pili, and that with FimU, PilE may couple the priming subcomplex to the major pilin PilA, allowing for efficient pilus assembly. Here we provide further support for this model, showing interaction of PilE with other minor pilins and the major pilin. A 1.25 Å crystal structure of PilEΔ1-28 shows a typical type IV pilin fold, demonstrating how it may be incorporated into the pilus. Despite limited sequence identity, PilE is structurally similar to Neisseria meningitidis minor pilins PilXNm and PilVNm, recently suggested via characterization of mCherry fusions to modulate pilus assembly from within the periplasm. A P. aeruginosa PilE-mCherry fusion failed to complement twitching motility or piliation of a pilE mutant. However, in a retraction-deficient strain where surface piliation depends solely on PilE, the fusion construct restored some surface piliation. PilE-mCherry was present in sheared surface fractions, suggesting that it was incorporated into pili. Together, these data provide evidence that PilE, the sole P. aeruginosa equivalent of PilXNm and PilVNm, likely connects a priming subcomplex to the major pilin, promoting efficient assembly of T4aP.

KEYWORDS:

Neisseria; Neisseria meningitidis; PilC1; PilY1; Pseudomonas aeruginosa (P. aeruginosa); X-ray crystallography; bacterial adhesion; bacterial pathogenesis; bacterial two-hybrid; minor pilins; pilus assembly; protein-protein interaction; twitching motility; type IV pili

PMID:
26359492
PMCID:
PMC4646338
DOI:
10.1074/jbc.M115.683334
[Indexed for MEDLINE]
Free PMC Article

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