title: Alterations of cellular physiology in Escherichia coli in response to oxidative phosphorylation impaired by defective F1-ATPase.
abstract: The physiological changes in an F1-ATPase-defective mutant of Escherichia coli W1485 growing in a glucose-limited chemostat included a decreased growth yield (60%) and increased specific rates of both glucose consumption (168%) and respiration (171%). Flux analysis revealed that the mutant showed approximately twice as much flow in glycolysis but only an 18% increase in the tricarboxylic acid (TCA) cycle, owing to the excretion of acetate, where most of the increased glycolytic flux was directed. Genetic and biochemical analyses of the mutant revealed the downregulation of many TCA cycle enzymes, including citrate synthase, and the upregulation of the pyruvate dehydrogenase complex in both transcription and enzyme activities. These changes seemed to contribute to acetate excretion in the mutant. No transcriptional changes were observed in the glycolytic enzymes, despite the enhanced glycolysis. The most significant alterations were found in the respiratory-chain components. The total activity of NADH dehydrogenases (NDHs) and terminal oxidases increased about twofold in the mutant, which accounted for its higher respiration rate. These changes arose primarily from the increased (3.7-fold) enzyme activity of NDH-2 and an increased amount of cytochrome bd in the mutant. Transcriptional upregulation appeared to be involved in these phenomena. As NDH-2 cannot generate an electrochemical gradient of protons and as cytochrome bd is inferior to cytochrome bo3 in this ability, the mutant was able to recycle NADH at a higher rate than the parent and avoid generating an excess proton-motive force. We discuss the physiological benefits of the alterations in the mutant.
authors.affiliation: Laboratory of Microbial Physiology, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan.
authors.forename: Sakiko
authors.initials: S
authors.lastname: Noda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Takezawa
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Mizutani
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Asakura
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Nishiumi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Onoe
authors.forename: Masaru
authors.initials: M
authors.lastname: Wada
authors.forename: Fusao
authors.initials: F
authors.lastname: Tomita
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Matsushita
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yokota
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D002952:Citric Acid Cycle; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis; D015151:Immunoblotting; D009154:Mutation; D009245:NADH Dehydrogenase / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010088:Oxidoreductases / Q000378:metabolism; D010101:Oxygen Consumption; D006180:Proton-Translocating ATPases / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; D010088:Oxidoreductases; D009245:NADH Dehydrogenase; D006180:Proton-Translocating ATPases; D005947:Glucose; D019342:Acetic Acid