A mutant Escherichia coli, selected for resistance to the antibiotic neomycin, was unable to utilize nonfermentable carbon sources for growth. Two strains were selected from this mutant on the basis of their ability to grow utilizing succinate as a carbon source. All three strains had approximately equal amounts of the Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3) protein, but the activity of the enzyme differed in each strain. The Mg2+-ATPase from each of the three strains lost activity upon solubilization and appeared to undergo rapid dissociation once solubilized. This dissociation is similar to that described for the wild type after cold exposure.
