title: ATP binding to the ϵ subunit of thermophilic ATP synthase is crucial for efficient coupling of ATPase and H+ pump activities.
abstract: ATP binding to the ϵ subunit of F1-ATPase, a soluble subcomplex of TFoF1 (FoF1-ATPase synthase from the thermophilic Bacillus strain PS3), affects the regulation of F1-ATPase activity by stabilizing the compact, ATPase-active, form of the ϵ subunit [Kato, S., Yoshida, M. and Kato-Yamada, Y. (2007) J. Biol. Chem. 282, 37618-37623]. In the present study, we report how ATP binding to the ϵ subunit affects ATPase and H+ pumping activities in the holoenzyme TFoF1. Wild-type TFoF1 showed significant H+ pumping activity when ATP was used as the substrate. However, GTP, which bound poorly to the ϵ subunit, did not support efficient H+ pumping. Addition of small amounts of ATP to the GTP substrate restored coupling between GTPase and H+ pumping activities. Similar uncoupling was observed when TFoF1 contained an ATP-binding-deficient ϵ subunit, even with ATP as a substrate. Further analysis suggested that the compact conformation of the ϵ subunit induced by ATP binding was required to couple ATPase and H+ pumping activities in TFoF1 unless the ϵ subunit was in its extended-state conformation. The present study reveals a novel role of the ϵ subunit as an ATP-sensitive regulator of the coupling of ATPase and H+ pumping activities of TFoF1.
authors.affiliation: Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Kadoya
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kato
authors.forename: Kei
authors.initials: K
authors.lastname: Watanabe
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kato-Yamada
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D001407:Bacillus / Q000201:enzymology / Q000378:metabolism; D001665:Binding Sites; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D017494:Proton Pumps / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D017494:Proton Pumps; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases