title: pKa of the essential Glu54 and backbone conformation for subunit c from the H+-coupled F1F0 ATP synthase from an alkaliphilic Bacillus.
abstract: 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.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Iván O
authors.initials: IO
authors.lastname: Rivera-Torres
authors.forename: Ray D
authors.initials: RD
authors.lastname: Krueger-Koplin
authors.forename: David B
authors.initials: DB
authors.lastname: Hicks
authors.forename: Sean M
authors.initials: SM
authors.lastname: Cahill
authors.forename: Terry A
authors.initials: TA
authors.lastname: Krulwich
authors.forename: Mark E
authors.initials: ME
authors.lastname: Girvin
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011522:Protons
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D011522:Protons; D018698:Glutamic Acid; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases