Title
F1F0-ATP Synthase BINDING OF δ SUBUNIT TO A 22-RESIDUE PEPTIDE MIMICKING THE N-TERMINAL REGION OF α SUBUNIT
Author
Joachim Weber, Alma Muharemagic, Susan Wilke-Mounts, Alan E. Senior
Year
2003
Journal
The Journal of Biological Chemistry
Abstract
The stator in F1F0-ATP synthase resists strain generated by rotor torque. In Escherichia coli theb 2δ subunit complex comprises the stator, bound to subunit a in F0 and to α3β3 hexagon of F1. Proteolysis and cross-linking had suggested that N-terminal residues of α subunit are involved in binding δ. Here we demonstrate that a synthetic peptide consisting of the first 22 residues of α (“αN1–22”) binds specifically to isolated wild-type δ subunit with high affinity (K d = 130 nM), accounting for a major portion of the binding energy when δ-depleted F1 and isolated δ bind together (K d = 1.4 nM). Stoichiometry of binding of αN1–22 to δ at saturation was 1/1, showing that in intact F1F0-ATP synthase only one of the three α subunits is involved in δ binding. When αN1–22 was incubated with δ subunits containing mutations in helices 1 or 5 on the F1-binding face of δ, peptide binding was impaired as was binding of δ-depleted F1. Residues α6–18 are predicted to be helical, and a potential helix capping box occurs at residues α3–8. Circular dichroism measurements showed that αN1–22 had significant helical content. Hypothetically a helical region of residues αN1–22 packs with helices 1 and 5 on the F1-binding face of δ, forming the α/δ interface.
Full Article
Instrument
J-710
Keywords
Circular dichroism, Secondary structure, Biochemistry