Role of recoverin in rod photoreceptor light adaptation

摘要

Key points class="unordered" style="list-style-type:disc" id="tjp12856-list-0001">Recoverin is a small molecular‐weight, calcium‐binding protein in rod outer segments that can modulate the rate of rhodopsin phosphorylation. We describe two additional and perhaps more important functions during photoreceptor light adaptation.Recoverin influences the rate of change of adaptation. In wild‐type rods, sensitivity and response integration time adapt with similar time constants of 150–200 ms. In Rv–/– rods lacking recoverin, sensitivity declines faster and integration time is already shorter and not significantly altered.During steady light exposure, rod circulating current slowly increases during a time course of tens of seconds, gradually extending the operating range of the rod. In Rv–/– rods, this mechanism is deleted, steady‐state currents are already larger and rods saturate at brighter intensities.We propose that recoverin modulates spontaneous and light‐activated phophodiesterase‐6, the phototransduction effector enzyme, to increase sensitivity in dim light but improve responsiveness to change in brighter illumination.