Fig. 1: Structural and functional overview of SthK.
From: Prolyl isomerization controls activation kinetics of a cyclic nucleotide-gated ion channel
a SthK ion channel (PDB: 6CJU) in surface (transparent gray) and cartoon representation. The separate domains of one monomer of the protein are shown in different colors with voltage-sensing domain (VSD): blue, pore domain: purple, C-linker: light green, and CNBD: cyan. Siphon is highlighted in orange. b Overlay of the CNBD of full-length SthK (PDB: 6CJU) in cyan and the isolated domain (PDB: 4D7T) in gray, with the siphons highlighted in orange and black, respectively. The central loop has residues in stick representation. cAMP is in stick representation (blue) for full-length SthK. c trans and cis conformer of a prolyl bond. d, e Quenching kinetics from the Tl+ flux assay for WT (d) and P300A (e) SthK. Samples were incubated with 0 µM cAMP (gray), and with 100 µM cAMP for 12 ms (black), 100 ms (blue), 500 ms (cyan) and 10 s (red, 5 s for SthK P300A). f Tl+ flux rates (Eqs. (2) and (3)) obtained from kinetics as shown in (d) and (e) for WT SthK (black, n = 8 independent experiments) and SthK P300A (blue, n = 5 independent experiments) as a function of the delay time. Symbols represent mean ± S.D. The activation time course (black curve) was fitted according to a double exponential function with amplitudes a and rate constants k of a1 = 0.5 ± 0.04, k1 = 160 ± 50 s−1, a2 = 0.45 ± 0.04, k2 = 2 ± 0.5 s−1. Source data are provided as a Source Data file.
