SCHOOL OF MEDICINE • DEPARTMENT OF MEDICINE

"Supramolecular protein engineering. Design of zinc-stapled insulin hexamers as a long-acting depot"
J Biol Chem. 2010 Feb 24
Phillips NB, Wan ZL, Whittaker L, Hu SQ, Huang K, Hua QX, Whittaker J, Ismail-Beigi F, Weiss MA.

Bottom-up control of supramolecular protein assembly can provide a therapeutic nanobiotechnology. We demonstrate that insulin's pharmacological properties can be enhanced by design of "zinc staples" between hexamers. Paired (i, i+4) His substitutions were introduced at an alpha-helical surface. The crystal structure contains both classical axial zinc ions and novel zinc ions at hexamer-hexamer interfaces. Although soluble at pH 4, the combined electrostatic effects of the substitutions and bridging zinc ions cause isoelectric precipitation at neutral pH. Following subcutaneous injection in a diabetic rat, the analog effected glycemic control with time course similar to that of long-acting formulation Lantus(R) Relative to Lantus, however, the analog discriminates at least 30-fold more stringently between the insulin receptor and mitogenic IGF receptor. Because aberrant mitogenic signaling may be associated with elevated cancer risk, such enhanced specificity may improve safety. Zinc stapling provides a general strategy to modify the pharmacokinetic and biological properties of a subcutaneous protein depot.