title: Sortase-mediated pilus fiber biogenesis in Streptococcus pneumoniae.
abstract: Streptococcus pneumoniae is a piliated pathogen whose ability to circumvent vaccination and antibiotic treatment strategies is a cause of mortality worldwide. Pili play important roles in pneumococcal infection, but little is known about their biogenesis mechanism or the relationship between components of the pilus-forming machinery, which includes the fiber pilin (RrgB), two minor pilins (RrgA, RrgC), and three sortases (SrtC-1, SrtC-2, SrtC-3). Here we show that SrtC-1 is the main pilus-polymerizing transpeptidase, and electron microscopy analyses of RrgB fibers reconstituted in vitro reveal that they structurally mimic the pneumococcal pilus backbone. Crystal structures of both SrtC-1 and SrtC-3 reveal active sites whose access is controlled by flexible lids, unlike in non-pilus sortases, and suggest that substrate specificity is dictated by surface recognition coupled to lid opening. The distinct structural features of pilus-forming sortases suggest a common pilus biogenesis mechanism that could be exploited for the development of broad-spectrum antibacterials.
authors.affiliation: Laboratoire des Protéines Membranaires, Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075 (CEA, CNRS, UJF, PSB), 41 rue Jules Horowitz, F-38027 Grenoble, France.
authors.forename: Clothilde
authors.initials: C
authors.lastname: Manzano
authors.forename: Carlos
authors.initials: C
authors.lastname: Contreras-Martel
authors.forename: Lamya
authors.initials: L
authors.lastname: El Mortaji
authors.forename: Thierry
authors.initials: T
authors.lastname: Izoré
authors.forename: Daphna
authors.initials: D
authors.lastname: Fenel
authors.forename: Thierry
authors.initials: T
authors.lastname: Vernet
authors.forename: Guy
authors.initials: G
authors.lastname: Schoehn
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Di Guilmi
authors.forename: Andréa
authors.initials: A
authors.lastname: Dessen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D036781:Fimbriae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D036781:Fimbriae Proteins