FUNCTIONAL ANALYSIS OF THE NIFA GAP DOMAIN OF AZOSPIRILLUM BRASILENSE: EFFECT OF TYR-PHE MUTATIONS IN NIFA AND INTERACTION OF THE MUTATED PROTEINS WITH GLNB USING THE YEAST TWO-HYBRID SYSTEM

摘要

NifA is synthesized both in conditions compatible and incompatible with nitrogen fixation in Azospirillum brasilense (Arsene et al., 1996). The mechanism by which NifA is converted from an active form to an inactive form is still unknown. However, itwas shown that GlnB is required to maintain NifA in its active form and the target of GlnB activity is the N-terminal part of NifA. The NifA N-terminal domain contains a GAF domain found in sensory proteins (Studholme and Dixon, 2003). Using the yeast two-hybrid system, it was shown that GlnB binds to NifA. In particular, GlnB interacts with the N-terminal GAF domain of NifA, but not with the central or C-terminal domains (Du et al., 2002; Chen et al., 2003).