title: Functional and idling rotatory motion within F1-ATPase.
abstract: ATP synthase mediates proton flow through its membrane portion, F0, which drives the synthesis of ATP in its headpiece, F1. The F1-portion contains a hexagonal array of three subunits alpha and three beta encircling a central subunit gamma, that in turn interacts with a smaller epsilon and with F0. Recently we reported that the application of polarized absorption recovery after photobleaching showed the ATP-driven rotation of gamma over at least two, if not three, beta. Here we extend probes of such rotation aided by a new theory for assessing continuous versus stepped, Brownian versus unidirectional molecular motion. The observed relaxation of the absorption anisotropy is fully compatible with a unidirectional and stepping rotation of gamma over three equidistantly spaced angular positions in the hexagon formed by the alternating subunits alpha and beta. The results strongly support a rotational catalysis with equal participation of all three catalytic sites. In addition we report a limited rotation of gamma without added nucleotides, perhaps idling and of Brownian nature, that covers only a narrow angular domain.
authors.affiliation: Abteilung Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, D-49069 Osnabrück, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Sabbert
authors.forename: S
authors.initials: S
authors.lastname: Engelbrecht
authors.forename: W
authors.initials: W
authors.lastname: Junge
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D016880:Anisotropy; D001703:Biophysics / Q000295:instrumentation / Q000379:methods*; D002736:Chloroplasts / Q000201:enzymology; D004800:Enzymes, Immobilized / Q000502:physiology; D004801:Eosine Yellowish-(YS); D007834:Lasers; D008958:Models, Molecular; D008962:Models, Theoretical; D015335:Molecular Probes; D009038:Motion; D009068:Movement / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000502:physiology* / Q000528:radiation effects; D018724:Spinacia oleracea / Q000201:enzymology
chemical_list: D004800:Enzymes, Immobilized; D015335:Molecular Probes; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D004801:Eosine Yellowish-(YS)