Apo-opsin exists in equilibrium between a predominant inactive and a rare highly active state

Shinya Sato, Beata Jastrzebska, Andreas Engel, Krzysztof Palczewski, Vladimir J. Kefalov

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Bleaching adaptation in rod photoreceptors is mediated by apo-opsin, which activates phototransduction with effective activity 10 5 -to 10 6 -fold lower than that of photoactivated rhodopsin (meta II). However, the mechanism that produces such low opsin activity is unknown. To address this question, we sought to record single opsin responses in mouse rods. We used mutant mice lacking efficient calcium feedback to boosts rod responses and generated a small fraction of opsin by photobleaching ~1% of rhodopsin. The bleach produced a dramatic increase in the frequency of discrete photoresponse-like events. This activity persisted for hours, was quenched by 11-cis-retinal, and was blocked by uncoupling opsin from phototransduction, all indicating opsin as its source. Opsin-driven discrete activity was also observed in rods containing non-activatable rhodopsin, ruling out transactivation of rhodopsin by opsin. We conclude that bleaching adaptation is mediated by opsin that exists in equilibrium between a predominant inactive and a rare meta II-like state. Significance Statement Electrophysiological analysis is used to show that the G-protein-coupled receptor opsin exists in equilibrium between a predominant inactive and a rare highly active state that mediates bleaching adaptation in photoreceptors.

Original languageEnglish
Pages (from-to)212-223
Number of pages12
JournalJournal of Neuroscience
Volume39
Issue number2
DOIs
StatePublished - Jan 9 2019

Keywords

  • Bleaching adaptation
  • G-protein-coupled receptor
  • GCAP
  • Opsin
  • Rhodopsin
  • Thermal activation

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