Experimental determination of control by the H(+)-ATPase in Escherichia coli.
Strains carrying deletions in the atp 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 an atp 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 on E. coli growth rate.
Jensen
P R
PR
Department of Microbiology, Technical University of Denmark, Lyngby.
Michelsen
O
O
Westerhoff
H V
HV
D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D017353:Gene Deletion; D005798:Genes, Bacterial; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D009876:Operon; D010101:Oxygen Consumption; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism
D013386:Succinates; D006180:Proton-Translocating ATPases; D005947:Glucose