title: Amyloid fibrillation of insulin under water-limited conditions.
abstract: Amyloid fibrillation in water-organic mixtures has been widely studied to understand the effect of protein-solvent interactions on the fibrillation process. In this study, we monitored insulin fibrillation in formamide and its methyl derivatives (formamide, N-methyl formamide, N,N-dimethyl formamide) in the presence and absence of water. These model solvent systems mimic the cellular environment by providing denaturing conditions and a hydrophobic environment with limited water content. Thioflavin T (ThT) assay revealed that binary mixtures of water with formamide and its methyl derivatives enhanced fibrillation rates and ?-sheet abundance, whereas organic solvents suppressed insulin fibrillation. We utilized solution small-angle x-ray scattering (SAXS) and differential scanning calorimetry (DSC) to investigate the correlation between protein-solvent interactions and insulin fibrillation. SAXS experiments combined with simulated annealing of the protein indicated that the degree of denaturation of the hydrophobic core region at residues B11-B17 determines the fibrillation rate. In addition, DSC experiments suggested a crucial role of hydrophobic interactions in the fibrillation process. These results imply that an environment with limited water, which imitates a lipid membrane system, accelerates protein denaturation and the formation of intermolecular hydrophobic interactions during amyloid fibrillation.
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
authors.forename: Tae Su
authors.initials: TS
authors.lastname: Choi
authors.affiliation: Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
authors.forename: Jong Wha
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
authors.forename: Kyeong Sik
authors.initials: KS
authors.lastname: Jin
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea; Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea. Electronic address: hughkim@postech.edu.
authors.forename: Hugh I
authors.initials: HI
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D057927:Hydrophobic and Hydrophilic Interactions; D007328:Insulin / Q000737:chemistry*; D008745:Methylation; D008969:Molecular Sequence Data; D066263:Protein Aggregation, Pathological; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D014867:Water / Q000737:chemistry
chemical_list: D007328:Insulin; D014867:Water