Organometallic iron: the key to biological hydrogen metabolism

X-ray crystallography of iron-hydrogenases reveals that the active-site H-c luster contains an unmistakably organometallic dinuclear iron subcluster. T he nickel-hydrogenases, which in general play different metabolic roles, ha ve a distinct but related active-site structure. The new structural definit ion, combined with chemical analogs and theoretical treatment, points towar d mechanistic understanding of iron-hydrogenases and the possibility of a u nified mechanism for all hydrogenases.