20 research outputs found
Ligand-Controlled Assembly of Hexamers, Dihexamers, and Linear Multihexamer Structures by the Engineered Acylated Insulin Degludec
Insulin degludec, an engineered acylated insulin, was
recently
reported to form a soluble depot after subcutaneous injection with
a subsequent slow release of insulin and an ultralong glucose-lowering
effect in excess of 40 h in humans. We describe the structure, ligand
binding properties, and self-assemblies of insulin degludec using
orthogonal structural methods. The protein fold adopted by insulin
degludec is very similar to that of human insulin. Hexamers in the
R<sub>6</sub> state similar to those of human insulin are observed
for insulin degludec in the presence of zinc and resorcinol. However,
under conditions comparable to the pharmaceutical formulation comprising
zinc and phenol, insulin degludec forms finite dihexamers that are
composed of hexamers in the T<sub>3</sub>R<sub>3</sub> state that
interact to form an R<sub>3</sub>T<sub>3</sub>–T<sub>3</sub>R<sub>3</sub> structure. When the phenolic ligand is depleted and
the solvent condition thereby mimics that of the injection site, the
quaternary structure changes from dihexamers to a supramolecular structure
composed of linear arrays of hundreds of hexamers in the T<sub>6</sub> state and an average molar mass, <i>M</i><sub>0</sub>,
of 59.7 Ă— 10<sup>3</sup> kg/mol. This novel concept of self-assemblies
of insulin controlled by zinc and phenol provides the basis for the
slow action profile of insulin degludec. To the best of our knowledge,
this report for the first time describes a tight linkage between quaternary
insulin structures of hexamers, dihexamers, and multihexamers and
their allosteric state and its origin in the inherent propensity of
the insulin hexamer for allosteric half-site reactivity