TAILIEUCHUNG - Báo cáo khoa học: A point mutation in the ATP synthase of Rhodobacter capsulatus results in differential contributions of DpH and Du in driving the ATP synthesis reaction

The interface between thec-subunit oligomer and the asubunit in the F0sector of the ATP synthase is believed to formthe core of the rotatingmotor powered by the protonic ¯ow. Besides the essential cAsp61 and aArg210 residues (Escherichia colinumbering), a few other residues at this interface, although nonessential, show a high degree of conservation, among these aGlu219. | Eur. J. Biochem. 269 1984-1992 2002 FEBS 2002 doi A point mutation in the ATP synthase of Rhodobacter capsulatus results in differential contributions of DpH and Du in driving the ATP synthesis reaction Paola Turina and B. Andrea Melandri Department of Biology Laboratory of Biochemistry and Biophysics University of Bologna Italy The interface between the c-subunit oligomer and the a subunit in the F0 sector of the ATP synthase is believed to form the core of the rotating motor powered by the protonic flow. Besides the essential cAsp61 and aArg210 residues Escherichia coli numbering a few other residues at this interface although nonessential show a high degree of conservation among these aGlu219. The homologous residue aGlu210 in the ATP synthase of the photosynthetic bacterium Rhodobacter capsulatus has been substituted by a lysine. Inner membranes prepared from the mutant strain showed approximately half of the ATP synthesis activity when driven both by light and by acid-base transitions. As estimated with the ACMA assay proton pumping rates in the inner membranes were also reduced to a similar extent in the mutant. The most striking impairment of ATP synthesis in the mutant a decrease as low as 12 times as compared to the wild-type was observed in the absence of a transmembrane electrical membrane potential Au at low transmembrane pH difference ApH . Therefore the mutation seems to affect both the mechanism responsible for coupling F1 with proton translocation by F0 and the mechanism determining the relative contribution of ApH and Au in driving ATP synthesis. Keywords ATP synthase mutagenesis Rhodobacter cap-sulatus ApH Au. Membrane-bound F0F1-ATPases ATP synthases catalyze ATP synthesis in bacteria chloroplasts and mitochondria at the expenses of an electrochemical potential gradient of protons or Na ions in some species . The membrane-embedded hydrophobic F0 sector is involved in proton translocation across the membrane and .

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