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

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. [ABSTRACT FROM AUTHOR]