Evolutionary tuning of rhodopsin-mediated light protection

Megabat rod rhodopsin retains nearly 60% of all-trans retinal at equilibrium by partitioning into Meta-III, providing extreme cytoprotection under daytime solar flux.

• Why it matters: Visual signaling through rhodopsin creates a risk of blinding photodamage, and existing models of dim-light protection overlook rapid arrestin quenching and reversible atRAL rebinding.
• What they did: The study compared dim-light specialists and engineered an active-state-locked signaling-null rhodopsin, then used partial-bleach co-incubation to test trans effects on wild-type regeneration and signaling.
• The result: Signaling-null sequestration achieved 100% atRAL sequestration, acted in trans to shield neighboring dark-state receptors, and human alleles linked to cytoprotective sequestration reduced blindness risk by 38%.

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