A monomeric insulin from the casiragua: molecular model building using computer graphics.

Interactive computer graphics have been used to construct a three-dimensional model of casiragua insulin assuming a tertiary structural homology with that of porcine insulin. The hydrophobic core of the molecule is conserved, but the hydrophobic surfaces involved in formation of dimers and hexamers in porcine insulin are more hydrophilic and contain charged residues. These observations are consistent with a close similarity of the far ultra violet circular dichroism of casiragua insulin and porcine insulin, and with the inability of casiragua insulin to self-associate. The low receptor-binding potency appears to result mainly from the substitution of B26-tyrosine by an arginine.