Crystal structures of Dronpa complexed with quenchable metal ions provide insight into metal biosensor development

Abstract

Many fluorescent proteins (FPs) show fluorescence quenching by specific metal ions, which can be applied towards metal biosensor development. In this study, we investigated the significant fluorescence quenching of Dronpa by Co2+ and Cu2+ ions. Crystal structures of Co2+-, Ni2+- and Cu2+ -bound Dronpa revealed previously unseen, unique, metal-binding sites for fluorescence quenching. These metal ions commonly interact with surface-exposed histidine residues (His194-His210 and His210-His212), and interact indirectly with chromophores. Structural analysis of the Co2+- and Cu2+- binding sites of Dronpa provides insight into FP-based metal biosensor engineering.