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Mutations in a Helix-1 Motif of the ATP Synthase c-Subunit of Bacillus pseudofirmus OF4 Cause Functional Deficits and Changes in the c-Ring Stability and Mobility on Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis

MPG-Autoren
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Preiss,  Laura
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Meier,  Thomas
Department of Structural Biology, Max Planck Institute of Biophysics, Max Planck Society;

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Zitation

Liu, J., Fackelmayer, O. J., Hicks, D. B., Preiss, L., Meier, T., Sobie, E. A., et al. (2011). Mutations in a Helix-1 Motif of the ATP Synthase c-Subunit of Bacillus pseudofirmus OF4 Cause Functional Deficits and Changes in the c-Ring Stability and Mobility on Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis. Biochemistry, 50(24), 5497-5506.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0024-D636-8
Zusammenfassung
The ATP synthase of the alkaliphile Bacillus pseudofirmus OF4 has a tridecameric c-subunit rotor ring. Each c-subunit has an AxAxAxA motif near the center of the inner helix, where neutralophilic bacteria generally have a GxGxGxG motif. Here, we studied the impact of four single and six multiple Ala-to-Gly chromosomal mutations in the A16xAxAxA22 motif on the capacity for nonfermentative growth and, for most of the mutants, on ATP synthesis by ADP- and Pi-loaded membrane vesicles at pH 7.5 and 10.5. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) analyses of the holo-ATP synthases were used to probe stability of the mutant c-rotors and mobility properties of the c-rotors as well as the monomeric c-subunits that are released from them by trichloroacetic acid treatment. Mutants containing an Ala16-to-Gly mutation exhibited the most severe functional defects. Via SDS–PAGE, most of the mutant c-monomers exhibited increased mobility relative to the wild-type (WT) c-subunit, but among the intact c-rings, only Ala16-to-Gly mutants exhibited significantly increased mobility relative to that of the WT c-ring. The hypothesis that these c-rings have a decreased c-subunit stoichiometry is still untested, but the functional impact of an Ala16-to-Gly mutation clearly depended upon additional Ala-to-Gly mutation(s) and their positions. The A16/20G double mutant exhibited a larger functional deficit than both the A16G and A16/18G mutants. Most of the mutant c-rings showed in vitro instability relative to that of the WT c-ring. However, the functional deficits of mutants did not correlate well with the extent of c-ring stability loss, so this property is unlikely to be a major factor in vivo.