title: Interaction and stoichiometry of the peripheral stalk subunits NtpE and NtpF and the N-terminal hydrophilic domain of NtpI of Enterococcus hirae V-ATPase.
abstract: The vacuolar ATPase (V-ATPase) is composed of a soluble catalytic domain and an integral membrane domain connected by a central stalk and a few peripheral stalks. The number and arrangement of the peripheral stalk subunits remain controversial. The peripheral stalk of Na+-translocating V-ATPase from Enterococcus hirae is likely to be composed of NtpE and NtpF (corresponding to subunit G of eukaryotic V-ATPase) subunits together with the N-terminal hydrophilic domain of NtpI (corresponding to subunit a of eukaryotic V-ATPase). Here we purified NtpE, NtpF, and the N-terminal hydrophilic domain of NtpI (NtpI(Nterm)) as separate recombinant His-tagged proteins and examined interactions between these three subunits by pulldown assay using one tagged subunit, CD spectroscopy, surface plasmon resonance, and analytical ultracentrifugation. NtpI(Nterm) directly bound NtpF, but not NtpE. NtpE bound NtpF tightly. NtpI(Nterm) bound the NtpE-F complex stronger than NtpF only, suggesting that NtpE increases the binding affinity between NtpI(Nterm) and NtpF. Purified NtpE-F-I(Nterm) complex appeared to be monodisperse, and the molecular masses estimated from analytical ultracentrifugation and small-angle x-ray scattering (SAXS) indicated that the ternary complex is formed with a 1:1:1 stoichiometry. A low resolution structure model of the complex produced from the SAXS data showed an elongated "L" shape.
authors.affiliation: Department of Biological Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan.
authors.forename: Misaki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Satoru
authors.initials: S
authors.lastname: Unzai
authors.forename: Shinya
authors.initials: S
authors.lastname: Saijo
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ito
authors.forename: Kenji
authors.initials: K
authors.lastname: Mizutani
authors.forename: Chiyo
authors.initials: C
authors.lastname: Suno-Ikeda
authors.forename: Yukako
authors.initials: Y
authors.lastname: Yabuki-Miyata
authors.forename: Takaho
authors.initials: T
authors.lastname: Terada
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Toyama
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Takuya
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Kakinuma
authors.forename: Ichiro
authors.initials: I
authors.lastname: Yamato
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
authors.forename: So
authors.initials: S
authors.lastname: Iwata
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murata
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016983:Enterococcus / Q000201:enzymology* / Q000235:genetics; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D025262:Vacuolar Proton-Translocating ATPases