Experimental determination of control by the H+-ATPase inEscherichia coli |
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Authors: | Peter Ruhdal Jensen Ole Michelsen Hans V Westerhoff |
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Institution: | (1) Department of Microbiology, Technical University of Denmark, Building 221, DK-2800 Lyngby, Denmark;(2) Department of Microbial Physiology, Free University, De Boelelaan 1087, NL-1081 HV Amsterdam, The Netherlands |
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Abstract: | Strains carrying deletions in theatp genes, encoding the H+-ATPase, were unable to grow on nonfermentable substrates such as succinate, whereas with glucose as the substrate the growth rate of anatp deletion mutant was surprisingly high (some 75–80% of wild-type growth rate). The rate of glucose and oxygen consumption of these mutants was increased compared to the wild-type rates. In order to analyze the importance of the H+-ATPase at its physiological level, the cellular concentration of H+-ATPase was modulated around the wild-type level, using genetically manipulated strains. The control coefficient by the H+-ATPase with respect to growth rate and catabolic fluxes was measured. Control on growth rate was absent at the wild-type concentration of H+-ATPase, independent of whether the substrate for growth was glucose or succinate. Control by the H+-ATPase on the catabolic fluxes, including respiration, was negative at the wild-type H+-ATPase level. Moreover, the turnover number of the individual H+-ATPase enzymes increased as the H+-ATPase concentration was lowered. The negative control by the H+-ATPase on catabolism may thus be involved in a homeostatic control of ATP synthesis and, to some extent, explain the zero control by the H+-ATPase onE. coli growth rate. |
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Keywords: | Oxidative phosphorylation respiration ATP fluxes Metabolic Control Analysis |
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