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E Billyard

Publications and source records attributed to E Billyard.

5 recordsLinked to original sources
PubMed1988

Pilin expression in Neisseria gonorrhoeae is under both positive and negative transcriptional control.

We have identified two closely linked genes, pilA and pilB, which act in trans on the pilin promoter. pilA-pilB map downstream of expression loci pilE1 and opaE1 in the gonococcal chromosome. Subcloning data indicate that pilB acts negatively on the pilin promoter, and insertional inactivation of pilB results in hyperpiliated gonococci. A pilA clone activates the pilin promoter in Escherichia coli, and a pilA-/pilA+ heterodiploid gonococcus exhibits a P- phenotype. Our inability to obtain simple pilA- mutants strongly suggests that pilA is an essential gene in the gonococcus. In an in vitro coupled transcription/translation system, inserts spanning the pilA and pilB region direct the synthesis of two proteins of 40 and 58 kd. DNA sequence analysis shows that the pilA and pilB loci encode proteins of 38.6 kd (with a putative DNA binding domain) and 57.9 kd respectively. The pilA and pilB genes are in opposite orientation relative to each other, and the 5' ends of the two genes overlap. We discuss how these two loci may interact to control pilin expression in the gonococcus.

Amino Acid Sequence↗
PubMed1985

Role of chromosomal rearrangement in N. gonorrhoeae pilus phase variation.

N. gonorrhoeae undergoes pilus phase and antigenic variation. During phase variation, the pilin gene is turned on and off at high frequencies. Two loci on the gonococcal chromosome from strain MS11 function as expression sites for the pilin gene (pilE1 and pilE2); many other sites apparently contain silent variant pilin sequences. We reported previously that during pilus phase variation, when cells switch from the pilus expressing state (P+) to the nonexpressing state (P-), genome rearrangement occurs. We have examined phase variation in more detail, and we report that in most P+ to P- switches a deletion of pilin gene information occurs in one or both expression sites. This deletion is due to either a simple or a multiple-step recombination event involving directly repeated sequences in the expression loci. The deletion explains the state of some P- cells, but not all. In the latter cells pilin expression is probably controlled by an undefined regulator.

Bacterial Outer Membrane Proteins↗
PubMed1984

Pilus genes of Neisseria gonorrheae: chromosomal organization and DNA sequence.

We have mapped two regions of the Neisseria gonorrheae genome, pilE1 and pilE2, which are involved in pilus expression. When the cells are in the piliated P+ state, these two loci carry sequences necessary for pilin production. A silent locus, pilS1, also maps near pilE1 and pilE2. pilS1 contains structural gene information but lacks pilus promoter sequences. The pilus gene sequences in pilE1 and pilE2 are identical in strain MS11.

Amino Acid Sequence↗
PubMedDate not supplied

Intragenic recombination leads to pilus antigenic variation in Neisseria gonorrhoeae.

The pilus of the bacterium Neisseria gonorrhoeae is a fimbriate surface structure which promotes attachment of the bacterium to host epithelial cells. Gonococcal pilus phase variation is characterized by a rapid on/off switch in which piliated (P+) cells throw off non-piliated (P-) variants and vice versa. Two regions of the gonococcal chromosome (pilE1 and pilE2) act as pilin expression loci, reminiscent of the MAT locus in the yeast Saccharomyces cerevisiae, while several other chromosomal regions contain silent (non-expressing) pilin sequences. Biochemical and antigenic diversity is seen in pili from a wide variety of clinical isolates. Pilins (pilus subunits) are composed of conserved N-terminal and variable C-terminal regions; the conserved region of gonococcal pilin is also found in pilins produced by widely disparate bacteria. We show here that the gonococcal pilin undergoes antigenic variation in vitro and in vivo. The protein consists of constant, semi-variable and hypervariable regions. This antigenic variation probably involves gene conversion of mini-cassettes of pilin information.

Amino Acid Sequence↗