Met-lead(1.59) is a genetically encoded fluorescent Pb[2+] indicator. It is a fusion protein consisting of a cyan fluorescent protein (ECFP ΔC11), the lead (Pb[2+]) binding domain (PbDB) (alpha helices 4-6) encoded by the PbrR gene from the bacterium Cupriavidus metallidurans CH34, and a yellow fluorescent protein (a circularly permuted form of Venus). The PbBDs form homodimers and thereby generate one pair of ion-binding sites at the two distant edges of the structure unit. Binding of Pb[2+] to the PbDBs results in significant conformational changes and enhances the fluorescence resonance energy transfer (FRET) between the two fluorescent proteins. (PMID: 22240981)