CRY2clust corresponds to the N-terminal photolyase homology region (PHR) of the Arabidopsis thaliana CRY2 gene (TAIR:28374), with a 9 amino acid extension (ARDPPDLDN) at the C-terminal end. The addition of this C-terminal extension substantially enhances the blue light-inducible clustering of the CRY2 PHR region, resulting in rapid and efficient oligomerization of CRY2clust when exposed to blue light. This property can be used to study protein interaction dynamics in vivo, and can also be used to transiently and reversibly control protein function in a light-dependent manner (PMID:28646204).