Abstract
The structure of the N-terminal-truncated Type IVb structural pilin (t-PilS) from Salmonella typhi was determined by NMR. Although topologically similar to the recently determined x-ray structure of pilin from Vibrio cholerae toxin-coregulated pilus, the only Type IVb pilin with known structure, t-PilS contains many distinct structural features. The protein contains an extra pair of beta-strands in the N-terminal alphabeta loop that align with the major beta-strands to form a continuous 7-stranded antiparallel beta-sheet. The C-terminal disulfide-bonded region of t-PilS is only half the length of that of toxin-coregulated pilus pilin. A model of S. typhi pilus has been proposed and mutagenesis studies suggested that residues on both the alphabeta loop and the C-terminal disulfide-bonded region of PilS might be involved in binding specificity of the pilus. This model structure reveals an exposed surface between adjacent subunits of PilS that could be a potential binding site for the cystic fibrosis transmembrane conductance regulator.
Highlights
Type IV pili have long been recognized as major bacterial virulence-associated adhesins that promote bacterial attachment to host cells [1]
DNA sequencing within the novel pathogenicity island (Salmonella pathogenicity island 7) identified a pil operon (11 genes, from PilL to PilV) that contains genes required for biosynthesis of Type IV pili in S. typhi [3]
Structure of S. typhi PilS—The construct used for the PilS structural determination is N-terminal-truncated (Met-26-Gly181, referred as t-PilS), and the truncation of the N-terminal 25 residues is necessary to prevent the pilin from oligomerization
Summary
Type IV pili have long been recognized as major bacterial virulence-associated adhesins that promote bacterial attachment to host cells [1]. The structural pilin protein (PilS) of the Type IV pili interacts with the first extracellular domain (residues 103–117) of CFTR [3,4,5].
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