p K a of the essential Glu54 and backbone conformation for subunit c from the H + ‐coupled F 1 F 0 ATP synthase from an alkaliphilic Bacillus

The conformation of the ATP synthase c‐subunit and the pK a 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 pK a of 7.7 is signif...

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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
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Summary:The conformation of the ATP synthase c‐subunit and the pK a 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 pK a of 7.7 is significantly higher than in non‐alkaliphiles, which likely prevents proton loss from the c‐rotor at high pH. The E54 pK a 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
1873-3468
DOI:10.1016/j.febslet.2004.08.049