Backbone resonance assignments of PhoCl, a photocleavable protein

PhoCl is a photocleavable protein engineered from a green-to-red photoconvertible fluorescent protein by circular permutation, and has been used in various optogenetic applications including precise control of protein localization and activity in cells. Upon violet light illumination, PhoCl undergoes a β-elimination reaction to be cleaved at the chromophore, resulting in spontaneous dissociation into a large empty barrel and a small C-terminal peptide. However, the structural determinants and the mechanism of the PhoCl photocleavage remain elusive, hindering the further development of more robust photocleavable optogenetic tools. Here, we report the backbone resonance assignments of PhoCl as a basis for studying the violet-light-induced self-cleavage mechanism of PhoCl.