The membrane ATPase of the (Mg, Ca)-ATPase-mutant E. coli K 12, strain AN 120.

In the (Mg,Ca)-ATPase-mutant E.coli K 12 strain AN 120, isolated by Butlin et a l.1, the acti­ vity of the membrane ATPase and of the ATPdependent transhydrogenase2 is greatly reduced. These cells are not able to grow on succinate or D-lactate because they lack oxidative phosphoryla­ tion. In the course of testing the properties of mem­ brane ATPase, we found, in addition to the reduc­ tion of activity, qualitative differences in the re­ maining ATPase activity with respect to the acti­ vation by Mg or Ca and the effect of salts.