Supplementary Figure 4: ACCuRET between an Anap site in the S1 helix and the transition metal ion site in the HCN domain.
From: The HCN channel voltage sensor undergoes a large downward motion during hyperpolarization
a, Cartoon showing the W218 Anap site and L186C modified by Cu2+-TETAC. b, Simultaneous current and Anap fluorescence recordings of spHCN-W218Anap channels. The Anap fluorescence did not change appreciably with -100 mV voltage pulses in the presence of 1 mM cAMP. c, Summary of the fractional Cu2+-TETAC quenching of Anap fluorescence at the W218 site, without and with the introduced cysteine L186C, at 0 mV and -100 mV (n = 4, error bars are s.e.m.). d, FRET efficiency calculated using the quenching data in panel c and Equation 1 (see Methods). e, Summary showing the distances of the W218/L186 FRET pair at 0 mV and -100 mV, calculated from the FRET efficiency in panel d and the FCG equation.
