Restoration of active transport in an Mg2+-adenosine triphosphatase-deficient mutant of Escherichia coli.

A neomycin-resistant mutant of Escherichia coli, NR70, lacking membrane-bound Mg(2+)-adenosine triphosphatase (EC 3.6.1.3) activity has been isolated. Both whole cells and membrane vesicles exhibit a reduced ability to accumulate amino acids and sugars. Other membrane-related functions such as oxygen consumption, the in vivo hydrolysis of o-nitrophenyl-beta-d-galactoside, and the phosphoenolpyruvate-dependent phosphotransferase system did not exhibit reduced activities in NR70. Amino acid transport could be partially restored by the addition of N,N'-dicyclohexylcarbodiimide. The results suggest that a role of the Mg(2+)-adenosine triphosphatase may be to participate in the coupling of energy derived from the electron transport chain to other processes such as transport.