Nitric oxide selectively releases metals from the <i>N</i> ‐terminal domain of metallothioneins: potential role at inflammatory sites

Abstract

ABSTRACT Metallothioneins (MTs) and various other metal binding proteins release metals when exposed to nitric oxide (NO). We investigated the structural consequences of the interaction between MTs and NO by using 1 H‐ and 113 Cd‐NMR spectroscopy and found that only the three metals from the N ‐terminal β‐domain were selectively released whereas the C ‐terminal α‐domain remains intact. Since it has been proposed that the β‐domain is responsible for the postulated role of MTs in zinc homeostasis, whereas the tight binding of metals in the α‐domain appears to play a role in heavy metal detoxification, our results suggest a potential regulatory role of NO in zinc distribution. Specifically, we present a mechanism whereby MT counteracts the cytotoxic effects of NO at inflammatory sites.