NMR Structure of Retinal Guanylate Cyclase Activating Protein 5 (GCAP5) with R22A Mutation That Abolishes Dimerization and Enhances Cyclase Activation.

Guanylate cyclase activating protein-5 (GCAP5) in zebrafish photoreceptors promotes the activation of membrane receptor retinal guanylate cyclase (GC-E). Previously, we showed the R22A mutation in GCAP5 (GCAP5) abolishes dimerization of GCAP5 and activates GC-E by more than 3-fold compared to that of wild-type GCAP5 (GCAP5). Here, we present ITC, NMR, and functional analysis of GCAP5 to understand how R22A causes a decreased dimerization affinity and increased cyclase activation.