- Metalloprotein Program Project Overview One-third of all proteins are metalloproteins , chemical combinations of protein atoms (carbon, nitrogen, oxygen, hydrogen, sulfur) with ions of metals such as iron, calcium, copper, and zinc. The hemoglobin, for example, that carries oxygen in the bloodstream, is an iron-containing metalloprotein. The metal ions in metalloproteins are critical to the ...www.scripps.edu/research/metallo