UCN119B (Protein unc-119 homolog B) belongs to the PDE6D/unc-119 family. This protein is enriched in the photoreceptors of the retina. It shares strong homology with the C. elegans unc119 protein and it can functionally complement the C. elegans unc119 mutation gene. The mammalian multisubunit photoreceptor cGMP phosphodiesterase PDE alpha beta gamma 2 (PDE6 family) is a peripherally membrane-associated enzyme. Recombinant human UNC119B protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.