| Popis: |
Two signal transduction cascades in B. japonicum, the FixLJ-FixK2 and the RegSR-NifA cascades, respond to micro-oxic conditions and mediate the expression of genes and operons concerned with microaerobic respiration, denitrification, heme biosynthesis, symbiotic nitrogen fixation, σ54 synthesis, chaperonin synthesis, and probably additional functions. How these cascades are integrated in a complex regulatory network is briefly reviewed here, with emphasis on some more recent data on the regulation of the nifA gene by the RegSR two-component system, and on new genes controlled by the NifA protein. Another complex network is that which controls the formation of the cellular chaperonin pool (GroES, GroEL). While the NifA protein appears to be instrumental in increasing the chaperonin pool size under nitrogen-fixing conditions, there are other transcriptional factors (σ32, HrcA) that act as key players in controlling GroESL synthesis after a heat shock. |
