Significance of Leu and Ser in the βDELSEED-loop of Escherichia coli ATP synthase

The current study investigated the significance of beta Leu-382 and beta Ser-383 residues in the highly conserved beta DELSEED-loop of Escherichia coli ATP synthase. E. coli wild type and mutant enzymes were inhibited by the honeybee venom peptide melittin, which is a known ATP synthase inhibitor. The wild type enzyme was fully inhibited by melittin. Melittin-induced inhibitory profiles of single mutants beta L382A/R/Q/D/E and beta S383A/R/Q/D/E followed the pattern of wild-type enzymes with 7% to 30% residual activity. Double mutants beta L382A/beta S383A, beta L382E/beta S383E, and beta L382R/beta S383R retained 30%, 80%, and 78% residual activity, respectively. Variable loss of oxidative phosphorylation was observed in mutant enzymes, which was also reflected in the comparative growth of wild type and mutant E. coli strains. Double mutant enzymes beta L382E/beta S383E and beta L382R/beta S383R showed significant resistance to the melittin-induced inhibition. Wild type and mutant E. coli strains showed variable loss of growth in the presence of melittin. Indicial growth loss of E. coli strains and inhibition of isolated ATP synthase suggested that beta Leu-382 and beta Ser-383 are vital for the function of enzyme. Individual loss of beta Leu-382 and beta Ser-383 does not affect the melittin-induced inhibition. However, loss of both beta Leu-382 and beta Ser-383 obstructs the inhibition suggesting loss of peptide binding at the beta DELSEED-loop of ATP synthase. (C) 2020 Elsevier B.V. All rights reserved.