Structure of a Pilin Monomer fromPseudomonas aeruginosa

Abstract

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 ␣-helix. Engineering of a truncated pilin from Pseudomonas 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 ␣-helix at the N terminus that lies across a 4-stranded antiparallel ␤-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.

Analysis of type IV pilus and its associated motility in Myxococcus xanthus using an antibody reactive with native pilin and pili

“…Additionally, the truncated PilA protein can be used for crystallization and structural studies. In P. aeruginosa strain K122-4, the pilin protein truncated in a similar way was found to retain the same overall structure as full-length pilin (Keizer et al, 2001). In M. xanthus the amino-sugars in extracellular polysaccharide have been proposed to be involved in the trigger of pilus retraction (Li et al, 2003).…”

“…This domain prohibits the overexpression and purification of PilA in its native form, and earlier efforts to purify overexpressed full-length M. xanthus PilA were unsuccessful . Truncation of Pseudomonas aeruginosa K122-4 pilin by removing the first 28 residues yielded a soluble protein retaining the overall structure and biological characteristics of intact pilin monomer (Keizer et al, 2001). Similarly, we engineered M. xanthus PilA to truncate it by the first 28 residues (Fig.…”

Structure of the Bundle-forming Pilus from Enteropathogenic Escherichia coli

“…The first high resolution structures of pilin proteins were those from the type IVa class, GC from N. gonorrhoeae (42), PAK and K122-4 from P. aeruginosa (39,40). The type IVa pilin structure is characterized by an extended N-terminal ␣-helix and a globular head domain that is folded into an ␣-␤ roll configuration (39,40,42). The globular head domain is well conserved and characterized by a four-stranded antiparallel continuous ␤-meander among all the type IVa pilins (36).…”

Use of Dominant-negative HrpA Mutants to Dissect Hrp Pilus Assembly and Type III Secretion in Pseudomonas syringae pv. tomato

“…For example, the structure of the F41 fragment of flagellin lacks 52 N-terminal residues and 44 C-terminal resides (40). Crystallization of type IV pilin subunits required the removal of an N-terminal region or the use of detergent (41)(42)(43)(44). The selfassembly of EspA and type I pilin was prevented by co-crystallization with its cognate chaperone or by the addition of a small "donor strand" peptide to an N-terminally truncated protein (37,(45)(46)(47).…”