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- Title
Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels.
- Authors
Kondapuram, Mahesh; Frieg, Benedikt; Yüksel, Sezin; Schwabe, Tina; Sattler, Christian; Lelle, Marco; Schweinitz, Andrea; Schmauder, Ralf; Benndorf, Klaus; Gohlke, Holger; Kusch, Jana
- Abstract
Hyperpolarization-activated and cyclic nucleotide (HCN) modulated channels are tetrameric cation channels. In each of the four subunits, the intracellular cyclic nucleotide-binding domain (CNBD) is coupled to the transmembrane domain via a helical structure, the C-linker. High-resolution channel structures suggest that the C-linker enables functionally relevant interactions with the opposite subunit, which might be critical for coupling the conformational changes in the CNBD to the channel pore. We combined mutagenesis, patch-clamp technique, confocal patch-clamp fluorometry, and molecular dynamics (MD) simulations to show that residue K464 of the C-linker is relevant for stabilizing the closed state of the mHCN2 channel by forming interactions with the opposite subunit. MD simulations revealed that in the K464E channel, a rotation of the intracellular domain relative to the channel pore is induced, which is similar to the cAMP-induced rotation, weakening the autoinhibitory effect of the unoccupied CL-CNBD region. We suggest that this CL-CNBD rotation is considerably involved in activation-induced affinity increase but only indirectly involved in gate modulation. The adopted poses shown herein are in excellent agreement with previous structural results. Interactions between opposite subunits of HCN channels are relevant for stabilizing the auto-inhibited state of the channel. Like cAMP-binding, K464E-mutation breaks these interactions to favor a channel's pre-activated state.
- Subjects
HELICAL structure; CARDIAC pacemakers; MOLECULAR dynamics; FLUORIMETRY; ROTATIONAL motion; MUTAGENESIS
- Publication
Communications Biology, 2022, Vol 5, Issue 1, p1
- ISSN
2399-3642
- Publication type
Article
- DOI
10.1038/s42003-022-03360-6