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How do cones get inactivated by dim light?

Asked by Tuqa Abdulsalam 

Cone photoreceptors use essentially the same molecular mechanisms of signal shutoff at the opsin level as rods. At this step cones achieve much higher speed of inactivation by employing, in addition to GRK1 and arrestin-1 used by rods, cone-specific GRK7 andarrestin-4. The presence of two GRKs speeds up the phosphorylation of light-activated opsin, whereas the expression of two arrestin subtypes with very different functional characteristics likely results in gradual switch from rapidly reversible arrestin-4 interaction with phospho-opsin at moderate light levels to semi-irreversible binding of arrestin-1 in very bright light. Inactivation at the transducin/PDE level is accelerated by 10-fold higher expression of RGS9-1 in cones.

(PDF) Phototransduction: Inactivation in Cones. Available from: [accessed May 07 2021].

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