Functional and idling rotatory motion within F-1-ATPase
|CHLOROPLAST ATP SYNTHASE; COUPLING FACTOR-I; DELTA-SUBUNIT; ESCHERICHIA-COLI F1-ATPASE; Multidisciplinary Sciences; MUTANT STRAINS; NUCLEOTIDE-BINDING; OXIDATIVE-PHOSPHORYLATION; PROPIONIGENIUM-MODESTUM; Science & Technology - Other Topics; SITE MECHANISM; THYLAKOID MEMBRANES
|NATL ACAD SCIENCES
|PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ATP synthase mediates proton flow through its membrane portion, F-0, which drives the synthesis of ATP in its headpiece, F-1. The F-1-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 F-0. 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 Brunnian nature, that covers only a narrow angular domain.
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checked on Feb 22, 2024