... on behalf of the Biochemical Society and distributed under the Creative Commons Attribution License 4.0 (CC BY) . ammonia excretion nitrogen fixation nitrogen regulation PII signal transduction proteins Nitrogen is an essential element for all living organisms as it is part of the building...

... the intracellular nitrogen regulation (Ntr) system to external changes in ammonium availability. Given the almost invariant coupling of AmtB and GlnK in bacteria and archaea it seems probable that these two proteins may constitute an ancestral nitrogen-responsive system that has been coupled with a variety...

..., University of Bristol, Bristol BS8 1TD, U.K. 2 To whom correspondence should be addressed (email ray.dixon@bbsrc.ac.uk ). 27 8 2004 © 2005 The Biochemical Society 2005 Figure 2 Nitrogen regulation of the NifL–NifA system ( a ) Structure of the E. coli PII signal-transduction...