1FNU:
reference: Structure of streptococcal pyrogenic exotoxin A reveals a novel metal cluster., Earhart CA, Vath GM, Roggiani M, Schlievert PM, Ohlendorf DH, Protein Sci 2000 Sep;9(9):1847-51. PMID: 11045630

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).