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J Biol Chem. 2015 Jan 2;290(1):601-11. doi: 10.1074/jbc.M114.616904. Epub 2014 Nov 11.

Pseudomonas aeruginosa minor pilins prime type IVa pilus assembly and promote surface display of the PilY1 adhesin.

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 L8N 3Z5, Canada.
2
the Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta T6G 2R3, Canada, the Provincial Laboratory for Public Health, Edmonton, Alberta T6G 2J2, Canada, and.
3
the Department of Biochemistry, Western University, London, Ontario N6A 3K7, Canada.
4
From the Department of Biochemistry and Biomedical Sciences and the Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario L8N 3Z5, Canada, burrowl@mcmaster.ca.

Abstract

Type IV pili (T4P) contain hundreds of major subunits, but minor subunits are also required for assembly and function. Here we show that Pseudomonas aeruginosa minor pilins prime pilus assembly and traffic the pilus-associated adhesin and anti-retraction protein, PilY1, to the cell surface. PilV, PilW, and PilX require PilY1 for inclusion in surface pili and vice versa, suggestive of complex formation. PilE requires PilVWXY1 for inclusion, suggesting that it binds a novel interface created by two or more components. FimU is incorporated independently of the others and is proposed to couple the putative minor pilin-PilY1 complex to the major subunit. The production of small amounts of T4P by a mutant lacking the minor pilin operon was traced to expression of minor pseudopilins from the P. aeruginosa type II secretion (T2S) system, showing that under retraction-deficient conditions, T2S minor subunits can prime T4P assembly. Deletion of all minor subunits abrogated pilus assembly. In a strain lacking the minor pseudopilins, PilVWXY1 and either FimU or PilE comprised the minimal set of components required for pilus assembly. Supporting functional conservation of T2S and T4P minor components, our 1.4 Å crystal structure of FimU revealed striking architectural similarity to its T2S ortholog GspH, despite minimal sequence identity. We propose that PilVWXY1 form a priming complex for assembly and that PilE and FimU together stably couple the complex to the major subunit. Trafficking of the anti-retraction factor PilY1 to the cell surface allows for production of pili of sufficient length to support adherence and motility.

KEYWORDS:

Adhesin; Bacterial Adhesion; Crystal Structure; Pilin; Pseudomonas aeruginosa (P. aeruginosa); Pseudopilin; Twitching Motility; Type II Secretion System (T2SS); Type IV Pili

PMID:
25389296
PMCID:
PMC4281761
DOI:
10.1074/jbc.M114.616904
[Indexed for MEDLINE]
Free PMC Article

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