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Structure of the minor pseudopilin XcpW from the Pseudomonas aeruginosa type II secretion system

Laura P Franz1, Badreddine Douzi, Eric Durand

  • 1Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.

Acta Crystallographica. Section D, Biological Crystallography
|January 20, 2011
PubMed

Insights

The structure of Pseudomonas aeruginosa pseudopilin XcpW(J) was determined, revealing insights into type II secretion. Deleting its disordered region did not impede virulence factor secretion.

Area of Science:

  • Microbiology
  • Structural Biology
  • Bacterial Secretion Systems

Background:

  • Pseudomonas aeruginosa uses type II secretion to export virulence factors.
  • Pseudopilins are key components of the type II secretion system, sharing homology with type IV pili.
  • Minor pseudopilins (XcpU, XcpV, XcpW, XcpX) form a complex at the pseudopilus tip.

Purpose of the Study:

  • To determine the high-resolution structure of the minor pseudopilin XcpW(J).
  • To understand the structural basis of pseudopilus formation and function in type II secretion.

Main Methods:

  • X-ray crystallography to determine the structure of XcpW(J) at 1.85 Å resolution.
  • In vivo functional analysis involving deletion of the disordered C-terminal region of XcpW(J).

Main Results:

  • The XcpW(J) structure exhibits a type IVa pilin fold with an extended antiparallel β-sheet.
  • This β-sheet may interact with other pseudopilins, potentially cradling N-terminal helices.
  • The C-terminal 31 amino acids of XcpW(J) are intrinsically disordered.
  • Deletion of this disordered region did not abolish type II secretion.

Conclusions:

  • The structure of XcpW(J) provides a molecular basis for its role in pseudopilus assembly.
  • The disordered C-terminal region of XcpW(J) is not essential for type II secretion function.
  • Further studies are needed to elucidate the precise roles of minor pseudopilins in complex formation and secretion initiation.

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