2GBA:
reference: Site-directed mutagenesis of proline 52 to glycine in amicyanin converts a true electron transfer reaction into one that is conformationally gated., Ma JK, Carrell CJ, Mathews FS, Davidson VL, Biochemistry. 2006 Jul 11;45(27):8284-93. PMID: 16819827

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