Regulation of Three Nitrogenase Gene Clusters in the Cyanobacterium Anabaena variabilis ATCC 29413

摘要: The filamentous cyanobacterium Anabaena variabilis ATCC 29413 fixes nitrogen under aerobic conditions in specialized cells called heterocysts that form response to an environmental deficiency combined nitrogen. Nitrogen fixation is mediated by the enzyme nitrogenase, which very sensitive oxygen. Heterocysts are microxic allow nitrogenase function a filament comprised primarily of vegetative produce oxygen photosynthesis. A. unique among well-characterized cyanobacteria it has three gene clusters encode different nitrogenases, conditions. nif1 genes Mo-nitrogenase functions only heterocysts, even filaments grown anaerobically. nif2 cells, but anoxic An alternative V-nitrogenase encoded vnf expressed environment deficient Mo. Thus, these nitrogenases differentially entire cluster, comprising at least 15 genes, control promoter for first gene, nifB1. Transcriptional many downstream occurs combination weak promoters within coding regions some and RNA processing, associated with increased transcript stability. show similar pattern transcriptional post-transcriptional expression suggesting complex regulation cluster conserved other cyanobacterial clusters.