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The Committee on Microbiology - Paper of the weekAmide bonds assemble pili on the surface of bacilli. Budzik, JM, Marraffini LA, Souda P, Whitelegge JP, Faull KF and Schneewind O. Proc Natl Acad Sci USA. 2008 Jul 22; 105(29): 10215-20. Pilin precursors are the building blocks of pili on the surface of Gram-positive bacteria; however, the assembly mechanisms of these adhesive fibers are unknown. Here, we describe the chemical bonds that assemble BcpA pilin subunits on the surface of Bacillus cereus. Sortase D cleaves BcpA precursor between the threonine (T) and the glycine (G) residues of its LPXTG sorting signal and catalyzes formation of an amide bond between threonine (T) of the sorting signal and lysine (K) in the YPKN motif of another BcpA subunit. Three CNA B domains of BcpA generate intramolecular amide bonds, and one of these contributes also to pilus formation. Conservation of catalysts and structural elements in pilin precursors in Gram-positive bacteria suggests a universal mechanism of fiber assembly. Committee on Microbiology, Department of Microbiology, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA. |
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