Amide-resolved hydrogen—deuterium exchange measurements from membrane-reconstituted polypeptides using exchange trapping and semiselective two-dimensional NMR

Summary

Amide-resolved, hydrogen-deuterium exchange from bee venom melittin reconstituted in fully hydrated vesicles suspended in D₂O buffer was measured using a technique involving (1) trapping samples throughout an exchange time course by rapid freezing and lyophilization; and (2) dissolving the dried peptide/lipid mixtures in deuteromethanol to record high-resolution spectra using semiselective excitation pulses to select peptide amide signals in the presence of large excess lipid signals. Two-dimensional, amide-selective GaussNOESY and fingerprint-selective off-diagonal PingCOSY spectra are shown to be suitable for rapid acquisition of amide-selective spectra, obtained throughout a time course of amide exchange in the membrane-bound state. Membrane-reconstituted melittin is shown to contain two sequences of exchange-stable amides, corresponding to helical regions on either side of the single proline residue.