A gene encoding the 16-kDa proteolipid subunit of Enterococcus hirae Na+-ATPase complex

Abstract By further sequencing the cloned genome DNA of Enterococcus hirae that retains the genes encoding two major subunits of Na + -transport ATPase (Takase, K., Yamato, I., and Kakinuma, Y. (1993) J. Biol. Chem. 268, 11610-11616), we found a gene, ntpK , encoding a very hydrophobic protein of 156 amino acids (Mr = 16,036). The amino acid sequence deduced from the ntpK gene matched with the partial sequence of a 16-kDa protein purified as the proteolipid component of Na + -ATPase. The amino acid sequence and the hydropathy profile of the NtpK product were very similar with those of the 16-kDa proteolipids of vacuolar (V-) H + -ATPases in eukaryotes. The amino-terminal half of this sequence was highly homologous to the carboxyl-terminal half, suggesting that it was evolved from a common ancestral gene through duplication. The proteolipid of E. hirae Na + -ATPase belongs to that of the eukaryotic V-ATPase.