Prolyl isomerization controls activation kinetics of a cyclic nucleotide-gated ion channel

Philipp A M Schmidpeter, Jan Rheinberger, Crina M Nimigean*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)
9 Downloads (Pure)

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.

Original languageEnglish
Article number6401
Number of pages12
JournalNature Communications
Volume11
Issue number1
DOIs
Publication statusPublished - 16-Dec-2020

Keywords

  • CIS-TRANS ISOMERASE
  • BINDING-PROTEIN
  • FK506-BINDING PROTEIN
  • RYANODINE RECEPTORS
  • LIGAND-BINDING
  • CYCLOSPORINE-A
  • CRYO-EM
  • CYCLOPHILIN
  • PROLINE
  • MODULATION

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