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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
Author(s) -
Rivera-Torres Iván O.,
Krueger-Koplin Ray D.,
Hicks David B.,
Cahill Sean M.,
Krulwich Terry A.,
Girvin Mark E.
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2004.08.049
Subject(s) - protein subunit , atp synthase gamma subunit , atp synthase , mutant , crystallography , chemistry , helix (gastropod) , stereochemistry , specificity factor , biophysics , biochemistry , enzyme , biology , atpase , ecology , atp hydrolysis , snail , gene , rna dependent rna polymerase , polymerase
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.