Rusticyanin

Rusticyanin is a copper-containing protein which is involved in electron-transfer, being a strong oxidant. It is a cupredoxin, or blue-copper protein due to its colour, and can be extracted from the bacteria Thiobacillus ferrooxidans. Similarly to other proteins of the same class, like plastocyanin, it contains a core β-sandwich fold and the binding site is a distorted tetrahedron consisting of four residues, two histidines, one cysteine and one methionine.