Book excerpt: This Handbook on Metalloproteins focuses on the available structural information of proteins and their metal ion coordination spheres. It centers on the metal ions indispensable for life but also considers metal ions used as substitution probes in studies of metalloproteins. Emphasizing the structure-function relationship, the book covers the common and distinct characterstics of metallo- enzymes, proteins, and amino acids bonded to copper, zinc, iron, and more.