Model of Ferredoxin from Rhodopseudomonas palustris based on the Protein Data Bank entry 4ID8: http://www.rcsb.org/pdb/explore/explore.do?structureId=4id8
"Ferredoxins are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions." --http://en.wikipedia.org/wiki/Ferredoxin
STL file created using VMD: http://www.ks.uiuc.edu/Research/vmd/
The protein backbone is represented in "cartoon" form. The cysteine residues and Fe3S4 cluster are represented as spheres.