The molecular switch that activates the cell wall anchoring step of pilus assembly in gram-positive bacteria.
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.
Mandlik
Anjali
A
Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA.
Das
Asis
A
Ton-That
Hung
H
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001704:Biopolymers / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D003353:Corynebacterium diphtheriae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron
D001426:Bacterial Proteins; D001704:Biopolymers; D008565:Membrane Proteins; D003546:Cysteine Endopeptidases
Infect Immun. 2004 May;72(5):2710-22
15102780
Infect Immun. 2006 Apr;74(4):2453-6
16552078
Science. 2007 Dec 7;318(5856):1625-8
18063798
Microbiol Mol Biol Rev. 2006 Mar;70(1):192-221
16524923
J Bacteriol. 2006 Sep;188(17):6318-25
16923899
Proc Natl Acad Sci U S A. 2006 Feb 21;103(8):2857-62
16481624
J Bacteriol. 2007 Apr;189(8):3156-65
17277070
Mol Microbiol. 2001 Jun;40(5):1049-57
11401711
Science. 2007 Dec 7;318(5856):1558-9
18063774
Mol Microbiol. 2007 Apr;64(1):111-24
17376076
Trends Microbiol. 2004 May;12(5):228-34
15120142
Trends Microbiol. 2008 Jan;16(1):33-40
18083568
Curr Opin Microbiol. 2000 Feb;3(1):65-72
10679419
Mol Microbiol. 2007 Oct;66(2):495-510
17897374
Res Microbiol. 2005 Apr;156(3):289-97
15808931
Mol Microbiol. 2007 Nov;66(4):961-74
17919283
Mol Microbiol. 2003 Nov;50(4):1429-38
14622427
Science. 2005 Jul 1;309(5731):105
15994549
Mol Microbiol. 2006 Oct;62(2):320-30
16978260
Mol Microbiol. 2006 Jun;60(6):1401-13
16796677
Nat Rev Microbiol. 2006 Jul;4(7):509-19
16778837
Mol Microbiol. 1990 Sep;4(9):1603-5
2287281
J Bacteriol. 2006 Feb;188(4):1526-33
16452436
Biochim Biophys Acta. 2004 Nov 11;1694(1-3):269-78
15546671
Mol Microbiol. 2004 Jul;53(1):251-61
15225319
Cell. 1992 Jul 24;70(2):267-81
1638631
Arch Oral Biol. 1974 Jan;19(1):71-9
4132890
Methods. 2000 Jan;20(1):111-26
10610809
J Clin Invest. 2006 Oct;116(10):2799-807
17016560
Infect Immun. 1976 Apr;13(4):1293-5
1279007