Cd2+ as a Ca2+ Surrogate in Protein–Membrane Interactions: Isostructural but Not Isofunctional

摘要: Due to its favorable spectroscopic properties, Cd(2+) is frequently used as a probe of Ca(2+) sites in proteins. We investigate the ability act structural and functional surrogate protein-membrane interactions. C2 domain from protein kinase Cα (C2α) was chosen paradigm for Ca(2+)-dependent phosphatidylserine-binding peripheral membrane domains. identified Cd(2+)-binding C2α using NMR spectroscopy, determined 1.6 A crystal structure Cd(2+)-bound C2α, characterized metal-ion-dependent interactions between phospholipid membranes fluorescence spectroscopy ultracentrifugation experiments. show that forms tight complex with membrane-binding loops but unable support function. This sharp contrast Pb(2+), which almost effective driving C2α-membrane association process. Our results provide first direct evidence specific role divalent metal ions mediating interactions, have important implications substitution studies proteins, illustrate potential diversity responses caused by toxic ions.