PMC:2726282 / 7780-9081 JSONTXT

{"project":"2_test","denotations":[{"id":"18599074-15465042-62517922","span":{"begin":1299,"end":1301},"obj":"15465042"},{"id":"18599074-10672184-62517922","span":{"begin":1299,"end":1301},"obj":"10672184"},{"id":"18599074-15504398-62517922","span":{"begin":1299,"end":1301},"obj":"15504398"}],"text":"However, other subnetworks are also worth mentioning. In particular, all nine TFs controlling the expression of genes for amino acid biosynthesis seem to be expressed constitutively by sigma 70. Each TF regulates the transcription of the required genes for producing different amino acids. At high concentrations of the amino acids, allosteric modifications of TFs follow binding to their respective amino acids, resulting in TF autorepression as well as to the repression of the corresponding biosynthetic genes. Interestingly, the logic behind negative autoregulation in this case is different from that of the catabolism of carbohydrates. While in the latter case TFs are autorepressed until the substrate is available, in the case of amino acids, TFs are autorepressed only in the presence of an excess of the synthesized final product. Another interesting subnetwork is that for alleviating the stresses by drugs, solvents and weak organic acids. The regulatory logic in this complex subnetwork is peculiar, as their components form multi-element circuits (see Fig. 3) and their inputs are directed by Rob and SoxR, two small proteins constitutively expressed but with very short half-lives (1–2 min). Their stability/degradation depends on the presence/absence of their effector signals.21,22,23"}