Interaction and reconstitution of carboxyl-terminal-shortened B chains with the intact A chain of insulin.
With the S-(thiomethyl)-A chain and despentapeptide (26-30) and desoctapeptide (23-30) S-(thiomethyl)-B chains of insulin at pH 10.8 and a molar ratio of A/B = 1.5, difference spectra of the mixed against the separated chains with negative peaks at 245 and 295 nm and a weak positive peak at 278 nm indicate interaction of the chains leading to Tyr environmental changes as in the case for the intact chains. With the shortened B chains, freshly dissolved from lyophilized powders, it takes some 2 h for the difference spectra to approach completion whereas with the solutions of the shortened B chains left standing overnight at pH 10.8 and 4 degrees C the difference spectra, similar in shape to that described above, appear almost immediately after mixing. Solvent perturbation with 20% ethylene glycol suggests some ordered structure for the despentapeptide but not for the desoctapeptide B chain. The interactions of the A chain with the shortened B chains appear to be weaker as compared to that with the intact B chain as shown by decreasing reconstitution yields for the intact, despentapeptide, and desoctapeptide B chains respectively with the A chain. The above results indicate that the C-terminal portion of the B chain is important not only for the activity of insulin but also for the correct pairing of the chains.
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004229:Dithiothreitol; D007328:Insulin; D007700:Kinetics; D046911:Macromolecular Substances; D008623:Mercaptoethanol; D010446:Peptide Fragments; D013056:Spectrophotometry, Ultraviolet; D013552:Swine
D007328:Insulin; D046911:Macromolecular Substances; D010446:Peptide Fragments; D008623:Mercaptoethanol; D004229:Dithiothreitol