title: Structure and function of vacuolar Na+-translocating ATPase in Enterococcus hirae.
abstract: A Na+-translocating ATPase was discovered in a gram-positive bacterium Enterococcus hirae. Our biochemical and molecular biological studies revealed that this Na+-ATPase belongs to the vacuolar-type enzyme. Purified Na+-ATPase consisted of nine subunits: NtpA, B, C, D, E, F, G, I, and K; reconstituted proteoliposomes showed ATP-driven electrogenic Na+ translocation. All these subunits were encoded by the ntp operon: ntpFIKECGABDHJ. The deduced amino acid sequences of the major subunits, A, B, and K (16 kDa proteolipid), were highly similar to those of A, B, and proteolipid subunits of vacuolar ATPases, although the similarities of other subunits were moderate. The ntpJ gene encoded a K+ transporter independent of the Na+-ATPase. Expression of this operon, encoding two transport systems for Na+ and K+ ions, was regulated at transcriptional level by intracellular Na+ as the signal. Two related cation pumps, vacuolar Na+-ATPase and F0F1, H+-ATPase, coexist in this bacterium.
authors.affiliation: Faculty of Pharmaceutical Sciences, Chiba University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: I
authors.initials: I
authors.lastname: Yamato
authors.forename: T
authors.initials: T
authors.lastname: Murata
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D027682:Cation Transport Proteins; D016983:Enterococcus / Q000201:enzymology* / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009876:Operon; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013329:Structure-Activity Relationship; D025262:Vacuolar Proton-Translocating ATPases
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D008565:Membrane Proteins; D017923:Sodium-Hydrogen Exchangers; D000251:Adenosine Triphosphatases; C098928:NtpJ protein, bacteria; D025262:Vacuolar Proton-Translocating ATPases; C021838:sodium-translocating ATPase; D006180:Proton-Translocating ATPases