The contribution of individual residues of an aggregative hexapeptide derived from the human γD-crystallin to its amyloidogenicity

Human gamma D-crystallin protein is abundant in the lens and is essential for preserving lens transparency. With age the protein may lose its native structure resulting in the formation of cataract. We recently reported an aggre-gative peptide, (41)Gly-Cys-Trp-Met-Leu-Tyr(46) from the human gamma D-crystallin, termed GDC6, exhibiting amyloi-dogenic properties in vitro. Here, we aimed to determine the contribution of each residue of the GDC6 to its amyloidogenicity. Molecular dynamic (MD) simulations revealed that the residues Trp, Leu, and Tyr played an important role in the amyloidogenicity of GDC6 by facilitating inter-peptide main-chain hydrogen bonds, and pi-pi interactions. MD predictions were further validated using single-, double-and triple-alanine-substituted GDC6 peptides in which their amyloidogenic propensity was individually evaluated using complementary biophysical techniques including Thioflavin T assay, turbidity assay, CD spectroscopy, and TEM imaging. Results revealed that the substitution of Trp, Leu, and Tyr together by Ala completely abolished aggregation of GDC6 in vitro, highlighting their importance in the amyloidogenicity of GDC6.

Automated summary

The specific residues of the human gamma D-crystallin protein were found to play an important role in the amyloidogenicity of GDC6, facilitating peptide-peptide interactions. By validating the amyloidogenic propensity of peptide variants, it was revealed that these specific residues are crucial for the amyloidogenicity of GDC6.