title: Conjugative pili of IncP plasmids, and the Ti plasmid T pilus are composed of cyclic subunits.
abstract: TrbC propilin is the precursor of the pilin subunit TrbC of IncP conjugative pili in Escherichia coli. Likewise, its homologue, VirB2 propilin, is processed into T pilin of the Ti plasmid T pilus in Agrobacterium tumefaciens. TrbC and VirB2 propilin are truncated post-translationally at the N terminus by the removal of a 36/47-residue leader peptide, respectively. TrbC propilin undergoes a second processing step by the removal of 27 residues at the C terminus by host-encoded functions followed by the excision of four additional C-terminal residues by a plasmid-borne serine protease. The final product TrbC of 78 residues is cyclized via an intramolecular covalent head-to-tail peptide bond. The T pilin does not undergo additional truncation but is likewise cyclized. The circular structures of these pilins, as verified by mass spectrometry, represent novel primary configurations that conform and assemble into the conjugative apparatus.
authors.affiliation: Max-Planck-Institut für Molekulare Genetik, Ihnestrasse 73, Dahlem, D-14195 Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Eisenbrandt
authors.forename: M
authors.initials: M
authors.lastname: Kalkum
authors.forename: E M
authors.initials: EM
authors.lastname: Lai
authors.forename: R
authors.initials: R
authors.lastname: Lurz
authors.forename: C I
authors.initials: CI
authors.lastname: Kado
authors.forename: E
authors.initials: E
authors.lastname: Lanka
mesh_terms: D016960:Agrobacterium tumefaciens; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D003227:Conjugation, Genetic; D017124:Conserved Sequence; D004926:Escherichia coli; D036781:Fimbriae Proteins; D018014:Gene Transfer Techniques; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D033903:Periplasmic Proteins; D018933:Pili, Sex / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D010957:Plasmids; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D037521:Virulence Factors
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D033903:Periplasmic Proteins; D011498:Protein Precursors; D037521:Virulence Factors; D036781:Fimbriae Proteins