title: Role of C-terminal negative charges and tyrosine residues in fibril formation of α-synuclein.
abstract: α-Synuclein (140 amino acids), one of the causative proteins of Parkinson's disease, forms amyloid fibrils in brain neuronal cells. In order to further explore the contributions of the C-terminal region of α-synuclein in fibril formation and also to understand the overall mechanism of fibril formation, we reduced the number of negatively charged residues in the C-terminal region using mutagenesis. Mutants with negative charges deleted displayed accelerated fibril formation compared with wild-type α-synuclein, demonstrating that negative charges located in the C-terminal region of α-synuclein modulate fibril formation. Additionally, when tyrosine residues located at position 125, 133, and 136 in the C-terminal region were changed to alanine residue(s), we found that all mutants containing the Tyr136Ala mutation showed delays in fibril formation compared with wild type. Mutation of Tyr136 to various amino acids revealed that aromatic residues located at this position act favorably toward fibril formation. In mutants where charge neutralization and tyrosine substitution were combined, we found that these two factors influence fibril formation in complex fashion. These findings highlight the importance of negative charges and aromatic side chains in the C-terminal region of α-synuclein in fibril formation.
authors.affiliation: Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University Tottori, 680-8552, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Izawa
authors.forename: Hironobu
authors.initials: H
authors.lastname: Tateno
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kameda
authors.forename: Kazuya
authors.initials: K
authors.lastname: Hirakawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Hato
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yagi
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Hongo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mizobata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawata
keywords: Amyloid; Parkinson's disease; amyloid formation mechanism; protein aggregation; site-directed mutagenesis; α-Synuclein