The crystal structures of three non-pancreatic human insulins.

X-ray studies on semi-synthetic human insulin have shown that it crystallizes in the rhombohedral space group R3 and is nearly isomorphous with 2 Zn pig insulin. Precession photographs of crystals of human and pig insulins show observable changes in the intensity patterns. Crystallographic analysis and refinement of semi-synthetic human insulin at 1.9 A resolution have shown that its molecular structure is very like that of pig insulin except at the C-terminus of the B chain where the change in sequence occurs. We also report the results of a high resolution crystallographic study of human insulins from different origins. The X-ray diffraction patterns of three non-pancreatic human insulins are indistinguishable from each other and from pancreatic human insulin. Refinement of the structures of the non-pancreatic human insulins has shown that they are identical within the limits of experimental error.