Control of Azospirillum brasilense NifA activity by PII:: effect of replacing Tyr residues of the NifA N-terminal domain on NifA activity

It was previously reported that the N-terminal domain of Azospirillum brasilense NifA was a negative regulator of the NifA activity and that the P-II protein prevented this inhibition under nitrogen fixing conditions, Here, we show that a mutation of a single Tyr residue at position 18 of the N-terminal domain of NifA led to an active NifA protein that did not require P-II for activation under nitrogen fixation conditions. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.