title: Haemophilus influenzae pili are composite structures assembled via the HifB chaperone.
abstract: Haemophilus influenzae is a Gram-negative bacterium that represents a common cause of human disease. Disease due to this organism begins with colonization of the upper respiratory mucosa, a process facilitated by adhesive fibers called pili. In the present study, we investigated the structure and assembly of H. influenzae pili. Examination of pili by electron microscopy using quick-freeze, deep-etch and immunogold techniques revealed the presence of two distinct subassemblies, including a flexible two-stranded helical rod comprised of HifA and a short, thin, distal tip structure containing HifD. Genetic and biochemical studies demonstrated that the biogenesis of H. influenzae pili is dependent on a periplasmic chaperone called HifB, which belongs to the PapD family of immunoglobulin-like chaperones. HifB bound directly to HifA and HifD, forming HifB-HifA and HifB-HifD complexes, which were purified from periplasmic extracts by ion-exchange chromatography. Continued investigation of the biogenesis of H. influenzae pili should provide general insights into organelle development and may suggest novel strategies for disease prevention.
authors.affiliation: Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA. stgeme@borcim.wustl.edu
authors.forename: J W
authors.initials: JW
authors.lastname: St Geme
authors.forename: J S
authors.initials: JS
authors.lastname: Pinkner
authors.forename: G P
authors.initials: GP
authors.lastname: Krasan
authors.forename: J
authors.initials: J
authors.lastname: Heuser
authors.forename: E
authors.initials: E
authors.lastname: Bullitt
authors.forename: A L
authors.initials: AL
authors.lastname: Smith
authors.forename: S J
authors.initials: SJ
authors.lastname: Hultgren
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D002458:Cell Fractionation; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology / Q000648:ultrastructure*; D005613:Freeze Etching; D017353:Gene Deletion; D005798:Genes, Bacterial; D006193:Haemophilus influenzae / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure*; D006801:Humans; D007251:Influenza, Human / Q000382:microbiology / Q000517:prevention & control; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D018832:Molecular Chaperones / Q000502:physiology* / Q000648:ultrastructure; D016296:Mutagenesis; D011485:Protein Binding
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C090992:HifA protein, Haemophilus influenzae; C090993:HifB protein, Haemophilus influenzae; C090011:HifD protein, Haemophilus influenzae; D018832:Molecular Chaperones; D036781:Fimbriae Proteins