6kk9

Publication Abstract from PubMed

Peptides and proteins self-assemble into beta-sheet-rich fibrils, amyloid, which extends its structure by incorporating peptide/protein molecules from solution. At the elongation edge, the peptide/protein molecule binds to the edge of the amyloid beta-sheet. Such processes are transient and elusive when observing molecular details by experimental methods. We used a model protein system, peptide self-assembly mimic (PSAM), which mimics an amyloid-like structure within a globular protein by capping both edges of single-layer beta sheet (SLB) with certain domains. We constructed a PSAM variant that lacks the capping domain on the C-terminal side to observe the structure of the beta-sheet edge of the peptide self-assembly. This variant, which we termed PSAM-edge, proved to be soluble with a monomeric form. Urea-induced unfolding experiments revealed that PSAM-edge displayed two-state cooperative unfolding, indicating the N-terminal capping domain and extended SLB folded as one unit. The crystal structure showed that SLB was almost completely structured except for a few terminal residues. A molecular dynamics simulation results revealed that the SLB structure was retained while the C-terminal four residues fluctuated, which was consistent with the crystal structure. Our findings indicate that SLB is stable even when one side of the beta-sheet edge is exposed to a solvent. This stability may prevent the dissociation of the attached peptide from the peptide self-assembly. Because of the scarcity of SLB proteins with exposed beta-sheet edges in nature, successful construction of the PSAM-edge expands our understanding of protein folding and design.

Structural analysis of the beta-sheet edge of peptide self-assembly using a model protein.,Shiga S, Makabe K Proteins. 2021 Feb 12. doi: 10.1002/prot.26063. PMID:33576533^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.