title: Phase variation of gonococcal pili by frameshift mutation in pilC, a novel gene for pilus assembly.
abstract: Pili prepared from Neisseria gonorrhoeae contain minor amounts of a 110 kd outer membrane protein denoted PilC. The corresponding gene exists in two copies, pilC1 and pilC2, in most strains of N.gonorrhoeae. In the piliated strain MS11(P+), only one of the genes, pilC2, was expressed. Inactivation of pilC2 by a mTnCm insertion resulted in a nonpiliated phenotype, while a mTnCm insertion in pilC1 had no effect on piliation. Expression of pilC was found to be controlled at the translational level by frameshift mutations in a run of G residues positioned in the region encoding the signal peptide. Nonpilated (P-), pilin expressing colony variants that did not express detectable levels of PilC were selected; all P+ backswitchers from these P-, PilC- clones were found to be PilC+. The structural gene for pilin, pilE, was sequenced and found to be identical in one P-, PilC- and P+, PilC+ pair. Most PilC- cells were completely bald whereas the PilC+ backswitcher had 10-40 pili per cell. Thus, a turn ON and turn OFF in the expression of PilC results in gonococcal pili phase variation. These results suggest that PilC is required for pilus assembly and/or translocation across the gonococcal outer membrane.
authors.affiliation: Department of Microbiology, University of Umea, Sweden.
authors.forename: A B
authors.initials: AB
authors.lastname: Jonsson
authors.forename: G
authors.initials: G
authors.lastname: Nyberg
authors.forename: S
authors.initials: S
authors.lastname: Normark
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology* / Q000648:ultrastructure; D016368:Frameshift Mutation; D005798:Genes, Bacterial; D014644:Genetic Variation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016254:Mutagenesis, Insertional; D009344:Neisseria gonorrhoeae / Q000235:genetics* / Q000502:physiology; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001425:Bacterial Outer Membrane Proteins; D015345:Oligonucleotide Probes; D036781:Fimbriae Proteins