Structural basis for delivery of the intact [Fe2S2] cluster by monothiol glutaredoxin.

Glutaredoxins (GRX) are redox proteins which use glutathione as a cofactor and are divided into two classes, monothiol and dithiol. In each class, several GRX have been shown to form [Fe2S2] cluster coordinating homodimers. The dithiol GRX homodimer is proposed to serve as a sequestration form and its iron-sulfur cluster as an oxidative stress sensor. In contrast, the monothiol GRX homodimer has been suggested to act as a scaffold for [Fe2S2] cluster delivery. We present here the structure of a monothiol GRX homodimer (Escherichia coli GRX4) coordinating a [Fe2S2] cluster that reveals the structural basis of intact iron-sulfur cluster delivery.