pKa of the essential Glu54 and backbone conformation for subunit c from the H+-coupled F1F0 ATP synthase from an alkaliphilic Bacillus

The conformation of the ATP synthase c-subunit and the pKa of its essential E54 residue were characterized in alkaliphilic Bacillus pseudofirmus OF4. The c-subunit folds as a helix-loop-helix, with inter-helical contacts demonstrated by paramagnetic relaxation effects. The E54 pKa of 7.7 is signific...

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Bibliographic Details
Published in:FEBS letters 2004-09, Vol.575 (1-3), p.131-135
Main Authors: Rivera-Torres, Iván O, Krueger-Koplin, Ray D, Hicks, David B, Cahill, Sean M, Krulwich, Terry A, Girvin, Mark E
Format: Article
Language:English
Subjects:
Bacillus - enzymology
Bacillus pseudofirmus
Bacterial Proteins - chemistry
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Glutamic Acid - chemistry
Hydrogen-Ion Concentration
Mitochondrial Proton-Translocating ATPases - chemistry
Mitochondrial Proton-Translocating ATPases - genetics
Mitochondrial Proton-Translocating ATPases - metabolism
Nuclear Magnetic Resonance, Biomolecular
Protein Conformation
Protein Folding
Protein Subunits - chemistry
Protein Subunits - genetics
Protein Subunits - metabolism
Protons
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Summary:The conformation of the ATP synthase c-subunit and the pKa of its essential E54 residue were characterized in alkaliphilic Bacillus pseudofirmus OF4. The c-subunit folds as a helix-loop-helix, with inter-helical contacts demonstrated by paramagnetic relaxation effects. The E54 pKa of 7.7 is significantly higher than in non-alkaliphiles, which likely prevents proton loss from the c-rotor at high pH. The E54 pKa was unchanged in a mutant, cP51A, that has a severe ATP synthesis defect at high pH only. cP51 must have some structural role that accounts for the mutant defect, such as different subunit-subunit interactions at high pH.
ISSN:0014-5793
DOI:10.1016/j.febslet.2004.08.049