Ultrahigh resolution and full-length pilin structures with insights for filament assembly, pathogenic functions, and vaccine potential.
Pilin proteins assemble into Type IV pili (T4P), surface-displayed bacterial filaments with virulence functions including motility, attachment, transformation, immune escape, and colony formation. However, challenges in crystallizing full-length fiber-forming and membrane protein pilins leave unanswered questions regarding pilin structures, assembly, functions, and vaccine potential. Here we report pilin structures of full-length DnFimA from the sheep pathogen Dichelobacter nodosus and FtPilE from the human pathogen Francisella tularensis at 2.3 and 1 Å resolution, respectively. The DnFimA structure reveals an extended kinked N-terminal α-helix, an unusual centrally located disulfide, conserved subdomains, and assembled epitopes informing serogroup vaccines. An interaction between the conserved Glu-5 carboxyl oxygen and the N-terminal amine of an adjacent subunit in the crystallographic dimer is consistent with the hypothesis of a salt bridge between these groups driving T4P assembly. The FtPilE structure identifies an authentic Type IV pilin and provides a framework for understanding the role of T4P in F. tularensis virulence. Combined results define a unified pilin architecture, specialized subdomain roles in pilus assembly and function, and potential therapeutic targets.
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
Sophia
S
Hartung
Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037.
Andrew S
AS
Arvai
Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037.
Timothy
T
Wood
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Subramaniapillai
S
Kolappan
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
David S
DS
Shin
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada. Electronic address: licraig@sfu.ca.
Lisa
L
Craig
Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720; Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037. Electronic address: jatainer@lbl.gov.
John A
JA
Tainer
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D001428:Bacterial Vaccines / Q000737:chemistry*; D018360:Crystallography, X-Ray / Q000379:methods; D020376:Dichelobacter nodosus / Q000737:chemistry*; D036781:Fimbriae Proteins / Q000737:chemistry* / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011108:Polymers / Q000737:chemistry; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D011108:Polymers; C063055:fimbrillin; D036781:Fimbriae Proteins