Glu residues of βDELSEED-motif are essential for peptide binding in Escherichia coli ATP synthase

The current study establishes the necessity of Glu-381, Glu-384, and Glu-385 in the βDELSEED-motif of Escherichia coli ATP synthase for peptide binding and inhibition. Inhibitory profiles of wild type and mutant E. coli membrane bound F₁F_o ATP synthase were studied in the presence and absence of C-terminal NH₂ bound melittin. Melittin-NH₂ caused almost complete inhibition of wild type ATPase, while partial inhibition was observed for mutants where Glu was replaced with Ala, Arg, or Gln. Additionally, melittin-NH₂ caused insignificant inhibition of a triple mutant where all three Glu residues were replaced with Ala residues, changing βDELSEED-motif to βDALSAAD-motif. Little or partial loss of oxidative phosphorylation in mutant strains corroborates their distinct location away from the catalytic site of ATP synthase. Moreover, abrogation of wild type E. coli cell growth and normal growth of mutant stains in the presence of melittin-NH₂ further validated the necessity of Glu residues in the βDELSEED-motif for peptide binding. Overall, while loss of one Glu residue at a time may allow partial peptide binding, loss of three Glu residues together-βE381, βE384, and βE385-is detrimental for peptide binding and inhibition of ATP synthase.