Document Detail

The molecular switch that activates the cell wall anchoring step of pilus assembly in gram-positive bacteria.
MedLine Citation:
PMID:  18779588     Owner:  NLM     Status:  MEDLINE    
Cell surface pili in gram-positive bacteria orchestrate the colonization of host tissues, evasion of immunity, and the development of biofilms. Recent work revealed that pilus assembly is a biphasic process wherein pilus polymerization is catalyzed by a pilus-specific sortase followed by cell wall anchoring of the pilus that is promoted by the housekeeping sortase. Here, we present molecular genetic and biochemical studies of a heterotrimeric pilus in Corynebacterium diphtheriae, uncovering the molecular switch that terminates pilus polymerization in favor of cell wall anchoring. The prototype pilus contains a major pilin (SpaA) forming the shaft, a tip pilin (SpaC), and another minor pilin (SpaB). Cells lacking SpaB form pilus fibers, but they are largely secreted in the medium, a phenotype also observed when cells lack the housekeeping sortase. Furthermore, the average pilus length is greatly increased in the absence of SpaB. Remarkably, a SpaB mutant that lacks the cell wall sorting signal but contains a critical lysine residue is incorporated in the pilus. However, the resulting pili fail to anchor to the cell wall. We propose that a specific minor pilin acts as the terminal subunit in pilus assembly. Cell wall anchoring ensues when the pilus polymer assembled on the pilus-specific sortase is transferred to the minor pilin presented by the housekeeping sortase via lysine-mediated transpeptidation.
Anjali Mandlik; Asis Das; Hung Ton-That
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2008-09-08
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  105     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2008 Sep 
Date Detail:
Created Date:  2008-09-17     Completed Date:  2008-10-09     Revised Date:  2014-09-10    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  14147-52     Citation Subset:  IM    
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MeSH Terms
Bacterial Proteins / genetics,  metabolism
Biopolymers / metabolism
Cell Wall / genetics,  metabolism*,  ultrastructure
Corynebacterium diphtheriae / cytology*,  genetics,  metabolism*
Cysteine Endopeptidases / genetics,  metabolism
Fimbriae, Bacterial / genetics,  metabolism*,  ultrastructure
Membrane Proteins / genetics,  metabolism
Microscopy, Electron, Transmission
Microscopy, Immunoelectron
Grant Support
Reg. No./Substance:
0/Bacterial Proteins; 0/Biopolymers; 0/Membrane Proteins; EC 3.4.22.-/Cysteine Endopeptidases
Comment In:
Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13703-4   [PMID:  18784365 ]

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