Neisseria gonorrhoeae PilC expression provides a selective mechanism for structural diversity of pili.
Pili of Neisseria gonorrhoeae undergo both phase and structural variation. Phase variation of gonococcal pili can be caused by a RecA-independent on/off switch in PilC, a protein involved in pilus biogenesis. We show here that spontaneous nonpiliated PilC- derivatives as well as PilC- insertional mutants have also acquired sequence alterations in pilE relative to the pilE gene of the piliated MS11mk(P+)-u parent, so that the pilin produced is processed to soluble S-pilin and can be released into the medium. It is proposed that pilin alterations are selected for in PilC- bacteria if the parental nonassembled pilin is toxic to the cells--i.e., is not degradable to S-pilin at rates sufficient to allow viability of the cells. Toxicity is indicated by the extreme instability of certain unassembled pilin sequences and by the low frequency of nonpiliated, pilin+, PilC- variants that emerge from piliated recA- cells. The presence of a point mutation changing leucine-39 to phenylalanine at the cleavage site for S-pilin in one nonpiliated, PilC-, recA- variant relative to its piliated parent is a further argument for a selective mechanism of structural diversity of the gonococcal pilin.
Jonsson
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AB
Department of Microbiology, University of Umeå, Sweden.
Pfeifer
J
J
Normark
S
S
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology* / Q000648:ultrastructure; D005798:Genes, Bacterial; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009344:Neisseria gonorrhoeae / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D015345:Oligonucleotide Probes; D011938:Rec A Recombinases / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D015345:Oligonucleotide Probes; D011993:Recombinant Fusion Proteins; C074063:pilE protein, Neisseria gonorrhoeae; D036781:Fimbriae Proteins; D011938:Rec A Recombinases