Structural Adaptability of Zinc Binding Sites: Different Structures in Partially, Fully, and Heavy‐Metal Loaded States

Abstract

The present study demonstrates that both the nature (Zn(II), Cd(II) or Hg(II)) and supply of metal ions determine whether zinc fingers fold into the well-known, fully loaded structures or alternatively populate a variety of structural states under substoichiometric conditions. Metal-bridged species are observed by perturbed angular correlation (PAC), EXAFS, UV spectroscopy, and stopped-flow kinetics. Transitions between structural states as adaptive reactions to changed metal-ion supply might represent intelligent system changes in zinc homeostasis, trafficking and signalling, and reflect features of heavy-metal toxicity at the molecular level. Because the zinc fingers exist in structural states that are different from the metal-free and fully loaded species, the prevailing view on metal-mediated molecular regulation in terms of "on and off control" might be oversimplified.