Fig. 2.

Electrophysiology and ss-NMR of DCD in the presence and absence of zinc ions. (A and B) Proton-decoupled ¹⁵N and (C) ²H ss-NMR spectra of 2 mol % [¹⁵N-Gly22,²H₃-Ala25]-DCD in oriented POPE/POPG without ZnCl₂ (A) and with fivefold molar excess of ZnCl₂ relative to the peptide concentration (B and C). ¹⁵NH₄Cl (40.0 ppm) and ²H₂O (0 Hz) were used as external references and the spectra processed with an exponential line broadening of 50 (A and B) and 500 Hz (C), respectively. The gray line in C shows a simulated spectrum arising from a 3° Gaussian distribution for the peptide alignment and a spectral line width of 2 kHz. (D) Current trace and point amplitude histogram representing DCD activity in 1 M NaCl, 5 mM Hepes, pH 7.1 recorded at a holding potential of +100 mV. Protein activity was only rarely observed under these conditions. (E and F) Current traces and point amplitude histograms of DCD-1L in 1 M NaCl, 3 mM ZnCl₂, 5 mM Hepes, pH 7.1 recorded at a holding potential of +100 mV; (E) 3.3 µM DCD-1L was added resulting in one defined conductance state. In (F) 7.9 µM DCD-1L was used and two distinct conductance levels each of about 80 pS were monitored, suggesting the insertion of two channels. (G) An event histogram of the conductance levels (n = 1,009) shows a mean conductance of G = (81 ± 14) pS. (H) Open lifetime analysis with τ = (4.4 ± 0.2) ms.