title: ATP-hydrolyzing excitation state of the reconstituted alpha 3 beta 3 complex of ATP synthase from the thermophilic bacterium PS3: structural characteristics shown by time-resolved small-angle X-ray scattering with synchrotron radiation.
abstract: The ATP-hydrolyzing excitation state of the alpha 3 beta 3 complex of the ATP synthase from the thermophilic bacterium PS3 was investigated using time-resolved small-angle X-ray scattering with synchrotron radiation. The results showed the presence of the alpha 3 beta 3 complex at a steady state during ATP hydrolysis when the alpha 3 beta 3 hexamer reacted with Mg-ATP. The radius of gyration of the complex in the steady state was significantly larger than that of the Mg-AMP-PNP-hexamer complex, indicating a conformational change to an expanded structure during catalysis. This alpha 3 beta 3 complex dissociated into alpha 1 beta 1 heterodimers with apparent first-order reaction kinetics after all the ATPs were converted to ADPs. In contrast, when the alpha 3 beta 3 complex reacted with Mg-ADP, the complex dissociated into dimers with apparent first-order reaction kinetics without showing the steady state of the complex. The dimers, however, re-associated into the hexamer when Mg-ATP was added. The results were well-explained by a computer simulation based on non-linear chemical dynamics, in which a reaction mechanism that incorporates the dynamic structure of the hexamer in the steady state was considered.
authors.affiliation: Institute for Protein Research, Osaka University.
authors.forename: M
authors.initials: M
authors.lastname: Sato
authors.forename: Y
authors.initials: Y
authors.lastname: Ito
authors.forename: M
authors.initials: M
authors.lastname: Harada
authors.forename: H
authors.initials: H
authors.lastname: Kihara
authors.forename: H
authors.initials: H
authors.lastname: Tsuruta
authors.forename: S
authors.initials: S
authors.lastname: Ohta
authors.forename: Y
authors.initials: Y
authors.lastname: Kagawa
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D001407:Bacillus / Q000201:enzymology*; D006868:Hydrolysis; D010446:Peptide Fragments / Q000737:chemistry*; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D012542:Scattering, Radiation; D017356:Synchrotrons; D013696:Temperature
chemical_list: D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases