Neuronal growth‐inhibitory factor (metallothionein‐3): reactivity and structure of metal–thiolate clusters*

Metallothionein-3, also called neuronal growth-inhibitory factor, is one of the four members of the mammalian metallothionein family, which in turn belongs to the metallothionein, a class of ubiquitously occurring low-molecular-weight cysteine- and metal-rich proteins containing metal-thiolate clusters. Mammalian metallothioneins contain two metal-thiolate clusters of the type M(II)(3)-Cys(9) and M(II)(4)-Cys(11) [or Cu(I)(4)-CysS(6-9)]. Although metallothionein-3 shares these metal clusters with the well-characterized metallothionein-1 and metallothionein-2, it shows distinct biological, structural and chemical properties. This short review focuses on the recent developments regarding the chemistry of the metal clusters in metallothionein-3, in comparison to those in metallothionein-1 and metallothionein-2, and discusses the possible biological and functional implications.