Structural evidence of thioacetate reduction by fluorescent protein mRuby

Red fluorescent protein mRuby is an important labelling tool for super-resolution imaging. With the addition of thioacetate, it was found here that the red colour of the protein aqueous solution changed, although still clear and transparent. Light spectrophotometry exhibited that, with the increase of thioacetate concentration, the absorption spectra changed abruptly. Crystallography showed the binding of thioacetate at the chromophore of mRuby. Atomic-resolution serial structures of mRuby single crystal showed snapshots of step-by-step reduction of thioacetate upon light irradiation. This observation suggests new insights for FP-compound interaction research and light energy harvesting for green chemistry.