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. Author manuscript; available in PMC: 2012 May 4.
Published in final edited form as: J Am Chem Soc. 2011 Apr 6;133(17):6681–6691. doi: 10.1021/ja111009s

Figure 1.

Figure 1

Illustration from the crystal structure of wild-type cytochrome c552 from Hydrogenobacter thermophilus (PDB 1YNR). The sulfur atom of Met61 occupies the sixth coordination site of the heme iron in the wild type. In the experiments, a Met61Ala mutation allowed the coordination of carbon monoxide in its place. The heme is covalently bound to the protein by two thioether linkages, tethering the vibrational probe to the protein even when it is unfolded.