RT Journal Article
SR Electronic
T1 Apo-Opsin Exists in Equilibrium Between a Predominant Inactive and a Rare Highly Active State
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 212
OP 223
DO 10.1523/JNEUROSCI.1980-18.2018
VO 39
IS 2
A1 Shinya Sato
A1 Beata Jastrzebska
A1 Andreas Engel
A1 Krzysztof Palczewski
A1 Vladimir J. Kefalov
YR 2019
UL http://www.jneurosci.org/content/39/2/212.abstract
AB Bleaching adaptation in rod photoreceptors is mediated by apo-opsin, which activates phototransduction with effective activity 105- to 106-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.