Oxidative phosphorylation in Escherichia coli K 12. Mutations affecting magnesium ion- or calcium ion-stimulated adenosine triphosphatase

摘要

p1. Two mutants of iEscherichia coli/i K 12 were isolated which, although able to grow on glucose, are unable to grow with succinate or d-lactate as the sole source of carbon. 2. Genetic mapping of these mutants showed that they both contain a mutation in a gene (designated iuncA/i) mapping at about minute 73.5 on the iE. coli/i chromosome. 3. The iuncA/isup-/sup alleles were transferred by bacteriophage-mediated transduction into another strain of iE. coli/i and the transductants compared with the parent strain to determine the nature of the biochemical lesion in the mutants. 4. The mutants gave low aerobic growth yields when grown on limiting concentrations of glucose, but oxidase activities in membranes from both the mutants and the normal strain were similar. 5. Measurement of P/O ratios with d-lactate as substrate indicated that a mutation in the iuncA/i gene causes uncoupling of phosphorylation associated with electron transport. 6. Determination of the Mgsup2+/sup,Casup2+/sup-stimulated adenosine triphosphatase activities in the mutant and normal strains indicated that the iuncA/i gene is probably the structural gene for Mgsup2+/sup,Casup2+/sup-stimulated adenosine triphosphatase. 7. Mgsup2+/sup,Casup2+/sup-stimulated adenosine triphosphatase therefore appears to be essential for oxidative phosphorylation in iE. coli/i./p