Investigating Cu(I) binding to model peptides of N-terminal Aβ isoforms

• Published in: Journal of inorganic biochemistry 2024-04, Vol.253, p.112480-112480, Article 112480
• Main Authors: Strausbaugh Hjelmstad, Abigail, Pushie, M. Jake, Ruth, Kaylee, Escobedo, Maria, Kuter, Kristin, Haas, Kathryn L.
• Format: Article
• Language: English
• Subjects: Amyloid beta; Amyloid beta-Peptides - chemistry; Chelating Agents; Copper - chemistry; Copper homeostasis; Humans; Ions; Metal binding constants; Model peptides; Protein Isoforms; UV–Vis; X-ray absorption spectroscopy
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2024.112480

Amyloid beta (Aβ) peptides and copper (Cu) ions are each involved in critical biological processes including antimicrobial activity, regulation of synaptic function, angiogenesis, and others. Aβ binds to Cu and may play a role in Cu trafficking. Aβ peptides exist in isoforms that vary at their C-and N-termini; variation at the N-terminal sequence affects Cu binding affinity, structure, and redox activity by providing different sets of coordinating groups to the metal ion. Several N-terminal isoforms have been detected in human brain tissues including Aβ1–40/42, Aβ3–42, pEAβ3–42, Aβ4–42, Aβ11–40 and pEAβ11–40 (where pE denotes an N-terminal pyroglutamic acid). Several previous works have individually investigated the affinity and structure of Cu(I) bound to some of these isoforms' metal binding domains. However, the disparately reported values are apparent constants collected under different sets of conditions, and thus an integrated comparison cannot be made. The work presented here provides the Cu(I) coordination structure and binding affinities of these six biologically relevant Aβ isoforms determined in parallel using model peptides of the Aβ metal binding domains (Aβ1–16, Aβ3–16, pEAβ3–16, Aβ4–16, Aβ11–16 and pEAβ11–16). The binding affinities of Cu(I)-Aβ complexes were measured using solution competition with ferrozine (Fz) and bicinchoninic acid (BCA), two colorimetric Cu(I) indicators in common use. The Cu(I) coordination structures were characterized by X-ray absorption spectroscopy. The data presented here facilitate comparison of the isoforms' Cu-binding interactions and contribute to our understanding of the role of Aβ peptides as copper chelators in healthy and diseased brains. A comparative analysis of Cu(I) coordination with model peptides representing various amyloid beta N-terminal isoforms reveals subtle differences in linear two-His binding structure. Isoforms with more histidine residues have higher affinity. Despite similar affinities, variation in solution heterogeneity is observed among certain isoforms, indicating subtle distinctions. [Display omitted] •Comparison of Cu(I) binding to six N-truncated amyloid beta (Aβ) model peptides.•Aβ Isoforms with 3 histidines (His) have stronger affinity than those with only two His.•Aβ Isoforms with position 3 N-terminus have increased heterogeneity in Cu(I) species.•Pyroglutamate Aβ isoforms demonstrate identical behavior to their glutamate analogues.•Isoforms show subtle differences in linear t