Isolation, purification and primary structure of insulin from the turtle Chrysemys dorbigni.

Insulin A and B chains from pancreas of the turtle Chrysemys dorbigni have been purified to homogeneity, and their primary structures have been determined. The sequence of the A chain is G-I-V-E-Q-C-C-H-N-T-C-S-L-Y-Q-L-E-N-Y-C-N, and that of the B chain is A-A-N-Q-H-L-C-G-S-H-L-V-E-A-L-Y-L-V-C-G-E-R-G-F-F-Y-S-P-K-A. The amino acid sequence of Chrysemys insulin is identical to that of another turtle (Pseudemys scripta), the chicken, and turkey. When compared with alligator insulin, it has three conservative substitutions in the B chain. However, there are seven substitutions when compared with the insulin of the rattlesnake.