8] Molecular structure of membrane-targeting calcium sensors in vision: Recoverin and guanylate cyclase-activating protein 2

Abstract

Publisher Summary An important class of calcium-binding proteins present in retinal photoreceptor cells includes recoverin from mammalian rods, guanylate cyclase-activating proteins (GCAP-1, GCAP-2, and GCAP-3) from mammalian rods and cones, and guanylate cyclase inhibitory protein (GCIP) from frog rods. The recoverin branch of the EF-hand superfamily includes neuronal Ca 2+ sensors such as neurocalcin, frequenin, and hippocalcin. Mass spectrometric analysis of retinal recoverin and the GCAP proteins revealed that they are myristoylated at the amino terminus. GCAP-2 exhibits different membrane-targeting properties from those of recoverin. The myristoylated and unmyristoylated forms of GCAP-2 bind to membranes at low Ca 2+ concentrations ( 50 mM NaCl).This chapter presents a detailed structural analysis of recoverin and GCAP-2. The Ca 2+ -induced structural changes in these proteins are important for elucidating their membrane-targeting mechanisms and for understanding the molecular mechanism of Ca 2+ -sensitive regulation of phototransduction.