Functional consequences of mutating candidate residues for Ca2+ association in the α7 nAChR.
(a) Left: For the mutation E158A, plot of the durations of individual channel openings in the presence of 10 µM ACh as a function of time of occurrence during the recording without or with 1.8 mM Ca2+. Recordings were obtained in the cell-attached patch configuration with an applied potential of −100 mV and Gaussian filter of 25 kHz. Left-middle: Comparison of the average channel opening frequency without or with 1.8 mM Ca2+, obtained from four to six patches for each condition; channel opening frequency is expressed relative to that in the presence of 1.8 mM Ca2+. Right-middle: Comparison of histograms of open dwell times fitted by the sum of two or three exponentials without or with 1.8 mM Ca2+, respectively. Right: Comparison of the average duration of channel openings without or with 1.8 mM Ca2+. (b and c) Results are shown as in a, but for the mutations E185Q and D160S, respectively. Error bars represent the SEM.