Prolyl isomerization controls activation kinetics of a cyclic nucleotide-gated ion channel. Academic Article uri icon

Overview

abstract

  • SthK, a cyclic nucleotide-modulated ion channel from Spirochaeta thermophila, activates slowly upon cAMP increase. This is reminiscent of the slow, cAMP-induced activation reported for the hyperpolarization-activated and cyclic nucleotide-gated channel HCN2 in the family of so-called pacemaker channels. Here, we investigate slow cAMP-induced activation in purified SthK channels using stopped-flow assays, mutagenesis, enzymatic catalysis and inhibition assays revealing that the cis/trans conformation of a conserved proline in the cyclic nucleotide-binding domain determines the activation kinetics of SthK. We propose that SthK exists in two forms: trans Pro300 SthK with high ligand binding affinity and fast activation, and cis Pro300 SthK with low affinity and slow activation. Following channel activation, the cis/trans equilibrium, catalyzed by prolyl isomerases, is shifted towards trans, while steady-state channel activity is unaffected. Our results reveal prolyl isomerization as a regulatory mechanism for SthK, and potentially eukaryotic HCN channels. This mechanism could contribute to electrical rhythmicity in cells.

publication date

  • December 16, 2020

Research

keywords

  • Cyclic Nucleotide-Gated Cation Channels
  • Spirochaeta

Identity

PubMed Central ID

  • PMC7744796

Scopus Document Identifier

  • 85097608640

Digital Object Identifier (DOI)

  • 10.1098/rstb.1982.0156

PubMed ID

  • 33328472

Additional Document Info

volume

  • 11

issue

  • 1