Occupancy of a C2-C2 type ‘Zinc-finger’ protein domain by copper Direct observation by electrospray ionization mass spectrometry☆

摘要: The metal ion specificity of most ‘zinc-finger’ binding domains is unknown. human estrogen receptor protein contains two different C2-C2 type sequences within its DNA-binding domain (ERDBD). Copper inhibits the function this by mechanisms which remain unclear. We have used electrospray ionization mass spectrometry to evaluate directly 71-residue ERDBD (K180-M250) in absence and presence Cu(II) ions. showed a high affinity for Cu was completely occupied with 4 bound; each evidently bound only ligand residues (net loss 2 Da per Cu). stoichiometry confirmed atomic absorption. These results (i) provide first direct physical evidence ability bind (ii) document twofold difference Zn- Cu-binding capacity. Differences structure Zn are predicted. Given relative intracellular contents Cu, our findings demonstrate need investigate further occupancy other zinc-finger both vitro vivo.