Structure and mechanism of vacuolar Na+-translocating ATPase from Enterococcus hirae.

V-type Na(+)-ATPase from Entercoccus hirae consists of nine kinds of subunits (NtpA(3), B(3), C(1), D(1), E(1-3), F(1-3), G(1), I(1), and K(10)) which are encoded by the ntp operon. The amino acid sequences of the major subunits, A, B, and K (proteolipid), were highly similar to those of A, B, and c subunits of eukaryotic V-ATPases, and those of beta, alpha, and c subunits of F-ATPases. We modeled the A and B subunits by homology modeling using the structure of beta and alpha subunits of F-ATPase, and obtained an atomic structure of NtpK ring by X-ray crystallography. Here we briefly summarize our current models of the whole structure and mechanism of the E. hirae V-ATPase.