Intramolecular amide bonds stabilize pili on the surface of bacilli.
Gram-positive bacteria elaborate pili and do so without the participation of folding chaperones or disulfide bond catalysts. Sortases, enzymes that cut pilin precursors, form covalent bonds that link pilin subunits and assemble pili on the bacterial surface. We determined the x-ray structure of BcpA, the major pilin subunit of Bacillus cereus. The BcpA precursor encompasses 2 Ig folds (CNA(2) and CNA(3)) and one jelly-roll domain (XNA) each of which synthesizes a single intramolecular amide bond. A fourth amide bond, derived from the Ig fold of CNA(1), is formed only after pilin subunits have been incorporated into pili. We report that the domains of pilin precursors have evolved to synthesize a discrete sequence of intramolecular amide bonds, thereby conferring structural stability and protease resistance to pili.
Budzik
Jonathan M
JM
Departments of Microbiology and Chemistry, University of Chicago, Chicago, IL 60637, USA.
Poor
Catherine B
CB
Faull
Kym F
KF
Whitelegge
Julian P
JP
He
Chuan
C
Schneewind
Olaf
O
D000577:Amides / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D036781:Fimbriae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000378:metabolism / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
D000577:Amides; D001426:Bacterial Proteins; D011498:Protein Precursors; D021122:Protein Subunits; D036781:Fimbriae Proteins; D014357:Trypsin