PHOSPHORYLATION AND FUNCTIONAL-ANALYSIS OF PILA, A PROTEIN INVOLVED IN THE TRANSCRIPTIONAL REGULATION OF THE PILIN GENE IN NEISSERIA-GONORRHOEAE

The transcriptional regulation of the pilE gene, coding for the pilin in Neisseria gonorrhoeae, by PilA/PilB proteins is quite complex. Sequ ence analysis of PilA suggested that it has multiple domains. PilA app ears to have in its N-terminal half a DNA-binding site followed by a r egion showing sequence similarity with other bacterial transcriptional regulators. In its C-terminal half, PilA has extensive homology with the 54 kDa protein of the eukaryotic signal-recognition particle which is involved in protein secretion. A transcriptional fusion between th e promoter of pilE and the lacZ gene was constructed and integrated in to the gonococcal chromosome. We show that transcription of the pilE-l acZ fusion is affected in pilA mutants in the absence of any possible interference with pilin secretion. Moreover, pilE transcription depend s on a -24/-12-type promoter which could be a member of a family of pr omoters recognized by the alternative sigma subunit, RpoN, of the RNA polymerase. We also show that PilA binds specifically to the promoter region of pilE and that it is phosphorylated in a manner dependent on acidic residues Glu-59, Asp-149 and Asp-186. The functional organizati on of PilA suggests that it may be an unusual transcriptional regulato r different from other RpoN-dependent activators.