Spontaneous Aggregation of the Insulin-Derived Steric Zipper Peptide VEALYL Results in Different Aggregation Forms with Common Features

Abstract

Recently, several short peptides have been shown to self-assemble into amyloid fibrils with generic cross-β spines, so-called steric zippers, suggesting common underlying structural features and aggregation mechanisms. Understanding these mechanisms is a prerequisite for designing fibril-binding compounds and inhibitors of fibril formation. The hexapeptide VEALYL, corresponding to the residues B12-17 of full-length insulin, has been identified as one of these short segments. Here, we analyzed the structures of multiple, morphologically different (fibrillar, microcrystal-like, oligomeric) [(13)C,(15)N]VEALYL samples by solid-state nuclear magnetic resonance complemented with results from molecular dynamics simulations. By performing NHHC/CHHC experiments, we could determine that the β-strands within a given sheet of the amyloid-like fibrils formed by the insulin hexapeptide VEALYL are stacked in an antiparallel manner, whereas the sheet-to-sheet packing arrangement was found to be parallel. Experimentally observed secondary chemical shifts for all aggregate forms, as well as Ø and ψ backbone torsion angles calculated with TALOS, are indicative of β-strand conformation, consistent with the published crystal structure (PDB ID: 2OMQ). Thus, we could demonstrate that the structural features of all the observed VEALYL aggregates are in agreement with the previously observed homosteric zipper spine packing in the crystalline state, suggesting that several distinct aggregate morphologies share the same molecular architecture.

Primary Nucleation Kinetics of Short Fibril-Forming Amyloidogenic Peptides

“…Solid-state NMR spectroscopy in combination with atomistic MD simulations in recent work 63 reveal that VEALYL peptides arrange in antiparallel β-sheets stacked parallel in a steric zipper structure. These authors have identified several aggregated states: disordered oligomeric, microcrystalline and fibrillar.…”

Inhibition of Insulin Amyloid Fibrillation by a Novel Amphipathic Heptapeptide

“…7 and supplemental Table S2) along seven consecutive residues in the insulin B chain ( 11 LVEALYL 17 ). This aggregation prone sequence is believed to be one of the driving forces behind insulin fibrillization as it forms a energetically favorable steric zipper in the insulin amyloid fiber (51,52). Several neighboring residues such as His-10, Cys-19, Gly-20, Glu-21, Gly-23, Phe-24, and Thr-27 in the B chain as well as a few residues in the A chain, namely Ser-12, Leu-13, Leu-16, Tyr-19, and Cys-20, also display substantial CSPs (supplemental Table S2).…”

DNA intercalators as amyloid assembly modulators: mechanistic insights

“…Transition of monomers to stable aggregates is accompanied by de-solvation of non-polar residues to form the amyloid core. 43,44 Such transition can be monitored by changes in hSAS along the reaction coordinate. 44 In control, the observation of a steep drop in hSAS within 50 ns was indicative of early burial of monomer side chains through hydrophobic interactions followed by a gradual decline till the end of simulation (Fig.…”

“…These observations complied with earlier experimental and theoretical reports documented on aggregation of short peptides. 18,20,43,44,52 FEL projections indicated spontaneous association of monomers to form higher order ensembles whereas an early single large basin was observed in FEL of IAP (22)(23)(24)(25)(26)(27)(28) and AGel (186-192) monomeric transitions into assembly in the presence of intercalators. Apparently, the kinetics of assembly formation in the presence of compounds was driven further owing to some topological advantage imparted by their planar groups.…”