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

• 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
• ISSN: 0014-5793
• DOI: 10.1016/j.febslet.2004.08.049

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.