Some features of the Streptococcus faecalis Na(+)-ATPase resemble those of the vacuolar-type ATPases

In the ethylenediaminetetraacetic acid (EDTA) extract prepared from the membranes of Streptococcus faecalis, we found the 330-kDa protein that was coordinately increased with the induction of Na(+)-ATPase. It was missed in the EDTA extract of Nak1, a mutant defective in the Na(+)-ATPase, but restored in that of its revertant, Nak1R. The 330-kDa protein showed the ATP hydrolytic activity by active staining, and mainly consisted of the polypeptides of 73 kDa, 52 kDa and possibly 38 kDa. In addition, the Na(+)-stimulated ATPase of the membranes was sensitive to both nitrate and N-ethylmaleimide, inhibitors for the vacuolar H(+)-ATPase. Thus, the Na(+)-ATPase of this organism has a structure similar to vacuolar H(+)-ATPase.