ComE, a competence protein from Neisseria gonorrhoeae with DNA-binding activity

Neisseria gonorrhoeae is naturally able to take up exogenous DNA and underg o genetic transformation. This ability correlates with the presence of func tional type IV pili, and uptake of DNA is dependent on the presence of a sp ecific IO-bp sequence, Among the known competence factors in N. gonorrhoeae , none has been shown to interact with the incoming DNA. Here we describe C omE, a DNA-binding protein involved in neisserial competence. The gene comE was identified through similarity searches in the gonococcal genome sequen ce, using as the query ComEA, the DNA receptor in competent Bacillus subtil is. The gene comE is present in four identical copies in the genomes of bot h :N.gonorrhoeae and Neisseria meningitidis, located downstream of each of the rRNA operons, Single-copy deletion of comE in N. gonorrhoeae did not ha ve a measurable effect on competence, whereas serial deletions led to gradu al decrease in transformation frequencies, reaching a 4 x 10(4)-fold reduct ion when all copies were deleted. Transformation deficiency correlated with impaired ability to take up exogenous DNA; however, the mutants presented normal piliation and twitching motility phenotype. The product of comE has 99 amino acids, with a predicted signal peptide; by immunodetection, a 8-kD a protein corresponding to processed ComE was observed in different strains of N. gonorrhoeae and N. meningitidis. Recombinant His-tagged ComE showed DNA binding activity, without any detectable sequence specificity. Thus, we identified a novel gonococcal DNA-binding competence factor which is neces sary for DNA uptake and does not affect pilus biogenesis or function.