PROTEIN STRUCTURE AND FOLDING
Structure of a Pilin Monomer fromPseudomonas aeruginosa: IMPLICATIONS FOR THE ASSEMBLY OF PILI*

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Type IV pilin monomers assemble to form fibers called pili that are required for a variety of bacterial functions. Pilin monomers oligomerize due to the interaction of part of their hydrophobic N-terminal α-helix. Engineering of a truncated pilin fromPseudomonas aeruginosa strain K122-4, where the first 28 residues are removed from the N terminus, yields a soluble, monomeric protein. This truncated pilin is shown to bind to its receptor and to decrease morbidity and mortality in mice upon administration 15 min before challenge with a heterologous strain of Pseudomonas. The structure of this truncated pilin reveals an α-helix at the N terminus that lies across a 4-stranded antiparallel β-sheet. A model for a pilus is proposed that takes into account both electrostatic and hydrophobic interactions of pilin subunits as well as previously published x-ray fiber diffraction data. Our model indicates that DNA or RNA cannot pass through the center of the pilus, however, the possibility exists for small organic molecules to pass through indicating a potential mechanism for signal transduction.

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Published, JBC Papers in Press, April 9, 2001, DOI 10.1074/jbc.M100659200

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This study was supported by the Canadian Bacterial Diseases Network, the Protein Engineering Network Centers of Excellence, the Canadian Institutes of Health Research, and Cytovax Biotechnologies Inc.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The atomic coordinates and the structure factors (code 1HPW) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).