Regulation of nitrogen fixation exam questions and answers

Regulation of nitrogen fixation exam questions and answers nif cluster - Answer- a genetically linked and coordinately regulated group of operons encoding genes required for nitrogen fixation What is the EBP for nif genes? - Answer- NifA How does the activity of NifA differ from that of NtrC? - Answer- The unmodified form of NifA is active NtrC needs to be phosphorylated to be active Under what 2 conditions does nif transcription occur? - Answer- 1) Only in the absence of a fixed nitrogen source 2) Only if oxygen concentration not high enough to damage nitrogenase What are the 3 major operons associated with nitrogen fixation and what molecules do they assimilate? - Answer- glnA - ammonium nas - nitrate nifA - nitrogen (via nitrogenase) Function of NifL - Answer- - FAD-containing redox center - Required for sensing intracellular Oxygen conc - When oxidised: inhibits ATPase activity of AAA+ domain of NifA -- prevents transcription of nif genes How does NifL sense intracellular oxygen concentrations? - Answer- - Senses oxygen levels indirectly by determining activity of electron transport chain - When oxygen sufficiently low -- NifL is reduced -- sequ