Retinal Guanylyl Cyclase-Activating Protein 1 and 2
Retinal guanylyl cyclases (RetGCs) in retinal rod and cone photoreceptors are regulated by a family of EF-hand Ca2+ sensor proteins called guanylyl cyclase-activating proteins (GCAP1-8) that belong to the neuronal calcium sensor (NCS) family. Mammalian GCAPs (GCAP1 and GCAP2) activate RetGCs at low Ca2+ levels in light-activated photoreceptor cells and inhibit RetGC activity at higher Ca2+ levels in dark-adapted photoreceptors. The Ca2+-sensitive RetGC activity controlled by GCAPs is an important mechanism of visual recovery and light adaptation of phototransduction. Mutations in either RetGCs or GCAPs that disable this Ca2+-sensitive cyclase activity are genetically linked to retinal disease. Here I review atomic-level structures of GCAP1 in both Ca2+-free/Mg2+-bound (activator) and Ca2+-saturated...