Open AccessPhenylalanine Mutation to Cyclohexylalanine Facilitates Triangular Trimer Formation by β-Hairpins Derived from Aβ
Author(s) -
Sepehr Haerianardakani,
Adam G. Kreutzer,
Patrick J. Salveson,
Tuan D. Samdin,
Gretchen Guaglia,
James S. Nowick
Publication year - 2020
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.0c09281
Subject(s) - chemistry , trimer , phenylalanine , mutation , stereochemistry , biochemistry , amino acid , organic chemistry , gene , dimer
Oligomers of the β-amyloid peptide, Aβ, play a central role in the pathogenesis and progression of Alzheimer's disease. Trimers and higher-order oligomers composed of trimers are thought to be the most neurotoxic Aβ oligomers. To gain insights into the structure and assembly of Aβ oligomers, our laboratory has previously designed and synthesized macrocyclic peptides derived from Aβ 17-23 and Aβ 30-36 that fold to form β-hairpins and assemble to form trimers. In this study, we found that mutating Phe 20 to cyclohexylalanine (Cha) in macrocyclic Aβ-derived peptides promotes crystallization of an Aβ-derived peptide containing the Aβ 24-29 loop (peptide 3 F20Cha ) and permits elucidation of its structure and assembly by X-ray crystallography. X-ray crystallography shows that peptide 3 F20Cha forms a hexamer. X-ray crystallography and SDS-PAGE further show that trimer 4 F20Cha , a covalently stabilized trimer derived from peptide 3 F20Cha , forms a dodecamer. Size exclusion chromatography shows that trimer 4 F20Cha forms higher-order assemblies in solution. Trimer 4 F20Cha exhibits cytotoxicity against the neuroblastoma cell line SH-SY5Y. These studies demonstrate the use of the F20Cha mutation to further stabilize oligomers of Aβ-derived peptides that contain more of the native sequence and thus better mimic the oligomers formed by full-length Aβ.