Coordinated regulation of gene expression by E ... - Jacobs University

RESULTS
phosphorylation, are associated with DNA relaxation. In contrast, the glyoxylate
bypass, which is predominantly utilized in aerobically growing cultures where most of
the energy is derived by glycolysis is activated by negative superhelicity (Figure 15 A
and Table 3). This suggests that high ATP/ADP ratios favouring supercoiling of DNA
by gyrase would facilitate glyoxylate bypass and plastic substrate synthesis, whereas
DNA relaxation would favour the production of ATP required to maintain gyrase
activity. Furthermore we found that the de novo pathway of nucleotide biosynthesis
explicitly involves the Hyp genes (Figure 15 B). Purine nucleotides are required during
fast growth and the dependence of this pathway on supercoiling levels is in keeping
with the prevailing conditions during fast growth. The data presented here thus shows
that supercoiling has a role not only in regulation of important individual genes but also
in coordinating the activity of metabolic pathways.
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