title: Characterization of the relationship between ADP- and epsilon-induced inhibition in cyanobacterial F1-ATPase.
abstract: The ATPase activity of chloroplast and bacterial F(1)-ATPase is strongly inhibited by both the endogenous inhibitor ε and tightly bound ADP. Although the physiological significance of these inhibitory mechanisms is not very well known for the membrane-bound F(0)F(1), these are very likely to be important in avoiding the futile ATP hydrolysis reaction and ensuring efficient ATP synthesis in vivo. In a previous study using the α(3)β(3)γ complex of F(1) obtained from the thermophilic cyanobacteria, Thermosynechococcus elongatus BP-1, we succeeded in determining the discrete stop position, ∼80° forward from the pause position for ATP binding, caused by ε-induced inhibition (ε-inhibition) during γ rotation (Konno, H., Murakami-Fuse, T., Fujii, F., Koyama, F., Ueoka-Nakanishi, H., Pack, C. G., Kinjo, M., and Hisabori, T. (2006) EMBO J. 25, 4596-4604). Because γ in ADP-inhibited F(1) also pauses at the same position, ADP-induced inhibition (ADP-inhibition) was assumed to be linked to ε-inhibition. However, ADP-inhibition and ε-inhibition should be independent phenomena from each other because the ATPase core complex, α(3)β(3)γ, also lapses into the ADP-inhibition state. By way of thorough biophysical and biochemical analyses, we determined that the ε subunit inhibition mechanism does not directly correlate with ADP-inhibition. We suggest here that the cyanobacterial ATP synthase ε subunit carries out an important regulatory role in acting as an independent "braking system" for the physiologically unfavorable ATP hydrolysis reaction.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Konno
authors.forename: Atsuko
authors.initials: A
authors.lastname: Isu
authors.forename: Yusung
authors.initials: Y
authors.lastname: Kim
authors.forename: Tomoe
authors.initials: T
authors.lastname: Murakami-Fuse
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sugano
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics; D006868:Hydrolysis; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases