Vortex-Induced Amyloid Superstructures of Insulin and Its Component A and B Chains

Abstract

Insulin is an amyloid-forming polypeptide built of two disulfide-linked chains (A and B), both themselves amyloidogenic. An interesting property of insulin is that agitation strongly influences the course of its aggregation, resulting in characteristic chiral superstructures of amyloid fibrils. Here, we investigate the self-assembly of these superstructures by comparing the quiescent and vortex-assisted aggregation of insulin and its individual A and B chains in the presence or absence of reducing agent tris(2-carboxyethyl)phosphine (TCEP). Our study shows that only the B chain in the presence of TCEP is converted into aggregates with morphology (according to atomic force microscopy) and optical activity (manifested as an extrinsic Cotton effect induced in bound thioflavin T) characteristic of amyloid superstructures that are normally formed by insulin in the absence of TCEP. In contrast to more rigid B-peptide fibrils, elongated aggregates of the A peptide become amorphous upon agitation. Moreover, the aggregation of equimolar mixture of both peptides does not produce highly ordered entities. Our results suggest that the dynamics of the B chain are the driving force for the assembly of superstructures, with the A chain being complicit as long as its own dynamics are controlled by the firm attachment to the B chain provided by the intact covalent structure of insulin.

Highly Amyloidogenic Two-chain Peptide Fragments Are Released upon Partial Digestion of Insulin with Pepsin

“…aggregation (50). Comparison of the re-association behavior of H-peptides under these two different sets of conditions would shed light on the possible role of disulfide bonds in their amyloidogenic propensity.…”

Chirality and Chiroptical Properties of Amyloid Fibrils

“…61 We have also shown that out of two component chains of insulin, A and B themselves amyloidogenic, only the latter one reveals a tendency to form chiral superstructures. 62 While the current understanding of structural prerequisites for selfassembly of such amyloid superstructures remains limited, the picture emerging from these two articles accentuates the role of tight and orderly lateral alignment of fibrils, which is the case of insulin amyloid provided by the C-terminal part of B-chains acting as molecular velcros. 61,62 More efforts must be made to explain the origins of the observed strong chiroptical properties of insulin amyloid superstructures.…”

Hydrodynamic and Thermophoretic Effects on the Supramolecular Chirality of Pyrene‐Derived Nanosheets

“…Both detection and induction of such chiroptical properties in the intentional absence of a chemical bias have been studied intensely over the past years 16. 20 However, very few researchers paid sufficient attention to the preparation methodology and correlation of the chiroptical response with final morphology of self‐assemblies 21. Recently, it has been shown that the pathway complexity of aggregation of the classic meso ‐tetra(4‐sulfophenyl) (TPPS) porphyrin influences the final chiroptical response 22…”