Ij. Mehr et al., A homologue of the recombination-dependent growth gene, rdgC, is involved in gonococcal pilin antigenic variation, GENETICS, 154(2), 2000, pp. 523-532
Neisseria gonorrhoeae pilin undergoes high-frequency changer; in primary am
ino acid sequence that aid in the avoidance of the host immune response and
alter pilus expression. The pilin amino acid changes reflect nucleotide ch
anges in the expressed gene, pilE, which result from nonreciprocal recombin
ation reactions with numerous silent loci, pilS A Series of mini-transposon
insertions affecting pilin antigenic variation were localized to three gen
es in one region of the cc chromosome. Mutational analysis with complementa
tion showed that a Gc gene with sequence similarity to the Escherichia coli
rdgC gene is involved in pilus-dependent colony phase variation and in pil
in antigenic variation. Furthermore, Mle show that the Gc rdgC homologue is
transcriptionally linked in an operon with a gene encoding a predicted GTP
ase. The inability to disrupt expression of this gene suggests it is an ess
ential gene (engA, essential neisserial GTPase). While some of the transpos
on mutations in rdgC anti insertions in the 5'-untranslated portion of engA
showed a growth defect, all transposon insertions investigated conferred a
n aberrant cellular morphology. Complementation analysis showed that the gr
owth deficiencies are due to the interruption of RdgC expression and not th
at of EngA. The requirement of RdgC for efficient pilin variation suggests
a role for this protein in specialized DNA recombination reactions.