Type IV pilus structure by cryo-electron microscopy and crystallography: implications for pilus assembly and functions.
Type IV pili (T4P) are long, thin, flexible filaments on bacteria that undergo assembly-disassembly from inner membrane pilin subunits and exhibit astonishing multifunctionality. Neisseria gonorrhoeae (gonococcal or GC) T4P are prototypic virulence factors and immune targets for increasingly antibiotic-resistant human pathogens, yet detailed structures are unavailable for any T4P. Here, we determined a detailed experimental GC-T4P structure by quantitative fitting of a 2.3 A full-length pilin crystal structure into a 12.5 A resolution native GC-T4P reconstruction solved by cryo-electron microscopy (cryo-EM) and iterative helical real space reconstruction. Spiraling three-helix bundles form the filament core, anchor the globular heads, and provide strength and flexibility. Protruding hypervariable loops and posttranslational modifications in the globular head shield conserved functional residues in pronounced grooves, creating a surprisingly corrugated pilus surface. These results clarify T4P multifunctionality and assembly-disassembly while suggesting unified assembly mechanisms for T4P, archaeal flagella, and type II secretion system filaments.
Craig
Lisa
L
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Volkmann
Niels
N
Arvai
Andrew S
AS
Pique
Michael E
ME
Yeager
Mark
M
Egelman
Edward H
EH
Tainer
John A
JA
D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000502:physiology; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D036781:Fimbriae Proteins / Q000737:chemistry; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000276:immunology; D011499:Protein Processing, Post-Translational; D016415:Sequence Alignment
D036781:Fimbriae Proteins