Possible Role of B8Gly in Insulin Structural Motif.

In the insulin structural motif n1-Cys-Gly-X10-Cys-n2-Cys-Cys-X3-Cys-X8-Cys-n3, there are seven absolutely conserved amino acid residues, and the only Gly is at position B8. When B8Gly was substituted with Ala by means of site-directed mutagenesis, a mutant insulin, [B8Ala]human insulin was obtained. The receptor binding capacity and in vivo biological activity of the [B8Ala]human insulin were about 2.5% and 10% of native porcine insulin, respectively. The far-UV circular dichroism (CD) spectra of [B8Ala]human insulin and human insulin showed that the relative content of alpha-helix in the mutant somewhat decreased. The results indicate that the B8Gly in the insulin structural motif is unreplaceble.