In-Planta Expression: Searching for the Genuine Chromophores of Cryptochrome-3 from Arabidopsis thaliana.

Göbel et al. present in this issue an exemplary study of identification of chromophores from Arabidopsis thaliana cryptochrome-3. Usually taken for granted, proteins and cofactors, respective chromophores, from heterologous expression are considered identical to material isolated from their genuine host. Cryptochromes carry two chromophores, an antenna cofactor and a functional flavin chromophore, both noncovalently embedded into the protein. In particular the antenna chromophore is loosely bound and often lost during protein purification. The authors identify from plant-extracted Cry3 unambiguously N ,N -methenyltetrahydrofolate as antenna chromophore and flavin adenine dinucleotide as the functional chromophore.