Some features of the Streptococcus faecalis Na+‐ATPase resemble thoseof the vacuolar‐type ATPases

Abstract

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 Nakl, a mutant defective in the Na⁺‐ATPase, but restored in that of its revertant, NaklR. 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.