657WTAPELL663 motif of the photoreceptor ROS-GC1: A general phototransduction switch

This study documents the identity of an intriguing transduction mechanism of the [Ca2+]i signals by the photoreceptor ROS-GC1. Despite their distal residences and operational modes in phototransduction, the two GCAPs transmit and activate ROS-GC1 through a common Ca2+ transmitter switch (Ca2+TS). A combination of immunoprecipitation, fluorescent spectroscopy, mutational analyses and reconstitution studies has been used to demonstrate that the structure of this switch is 657WTAPELL663. The two Ca2+ signaling GCAP pathways converge in Ca2+TS, get transduced, activate ROS-GC1, generate the LIGHT signal second messenger cyclic GMP and yet functionally perform divergent operations of the phototransduction machinery. The findings define a new Ca2+-modulated photoreceptor ROS-GC transduction model; it is depicted and discussed for its application to processing the different shades of LIGHT.

► Documents identity of an intriguing transduction mechanism of the [Ca2+]i signals by the photoreceptor ROS-GC1. ► Mechanism has a Core and Specific Impact on the signal transduction field. ► Core Impact. It exposes a common structural transduction switch through which all cyclases function. ► Specific Impact. Provides a function-specific mechanism for the switch in photoreceptor machinery. ► Defines a model how the switch senses and processes different shades of light.