The goal of the proposed research is to obtain a better understanding of the regulatory mechanisms we have found to function in the intact cell, especially the hierarchy among alternative control mechanisms and the domains of action of these control mechanisms in coordinating the activity of various metabolic pathways. In these studies the intact Escherichia coli cell serves as an elegant model system. The two focal points of our investigations will be further studies of: 1) the adenylate energy charge-hexose phosphate system of allosteric control that we have uncovered in the coordinate regulation of glycogen synthesis, glycolysis and glucose utilization, and 2) the 3',5'-cyclic AMP/guanosine 3'-diphosphate 5'-diphosphate system of coordinate regulation of glycogen, nucleic acid and protein synthesis we uncovered. We will continue to quantitatively correlate measured changes of in vivo levels of effector molecules with changes in the in vivo activity of key regulatory enzymes. An important question that has arisen from our previous work is why is there so much regulatory redundancy? E.g., glycogen synthesis in the intact E. coli cell can be increased by increases in hexose phosphate allosteric activators, decreases in inhibitory messenger nucleotides or by increases in stimulatory messenger nucleotides, all of which act to increase the velocity of ADP-glucose synthetase, the rate-limiting enzyme of bacterial glycogen synthesis. Each of these signals coordinates glycogen synthesis with various metabolic pathways. Our work has indicated that in different conditions different coordinating links are called upon, so that fluxes through the appropriate group of pathways are coordinated for the particular type of nutritional alteration. A major thrust of future work is to fill in our knowledge about the relative importance (hierarchy) of various redundant regulatory mechanisms for a particular metabolic pathway (e.g., glycogen synthesis) and how regulatory redundancy functions to coordinate the activity of the particular pathway with other pathways (domains of action).
| Roth, W G; Leckie, M P; Dietzler, D N (1988) Restoration of colony-forming activity in osmotically stressed Escherichia coli by betaine. Appl Environ Microbiol 54:3142-6 |
| Roth, W G; Porter, S E; Leckie, M P et al. (1985) Restoration of cell volume and the reversal of carbohydrate transport and growth inhibition of osmotically upshocked Escherichia coli. Biochem Biophys Res Commun 126:442-9 |
| Leckie, M P; Tieber, V L; Porter, S E et al. (1985) Independence of cyclic AMP and relA gene stimulation of glycogen synthesis in intact Escherichia coli cells. J Bacteriol 161:133-40 |
| Roth, W G; Leckie, M P; Dietzler, D N (1985) Osmotic stress drastically inhibits active transport of carbohydrates by Escherichia coli. Biochem Biophys Res Commun 126:434-41 |
