A hybrid adenosinetriphosphatase composed of F1 of Escherichia coli and F0 of Propionigenium modestum is a functional sodium ion pump.

Analyses on immunoblots indicated strong binding of the alpha- and beta-subunits of the ATPase of Propionigenium modestum to antibodies raised against the corresponding subunits of the F1F0 ATPase of Escherichia coli. Cross-reactivities of antibodies against the other ATPase subunits were not observed. The use of Na+ or H+ as alternate coupling ions, observed previously for the P. modestum ATPase [Laubinger, W., & Dimroth, P. (1989) Biochemistry 28, 7194-7198], is not found for the F1F0 ATPase of E. coli, which is specific for protons. However, a hybrid consisting of the F1 moiety of the E. coli ATPase and F0 of that from P. modestum performed Na+ or H+ transport in a reconstituted system. As with the homologous ATPase of P. modestum, H+ pumping of the hybrid was abolished at Na+ concentrations of greater than 1 mM. The F0 sector and not F1, therefore, determines the cation specificity of these F1F0 ATPases.