Direct Competition of ATCUN Peptides with Human Serum Albumin for Copper(II) Ions Determined by LC-ICP MS

Andra Noormägi; Tatjana Golubeva; Elina Berntsson; Sebastian K T S Wärmländer; Vello Tõugu; Peep Palumaa

doi:10.1021/acsomega.3c04649

Direct Competition of ATCUN Peptides with Human Serum Albumin for Copper(II) Ions Determined by LC-ICP MS

ACS Omega. 2023 Sep 7;8(37):33912-33919. doi: 10.1021/acsomega.3c04649. eCollection 2023 Sep 19.

Authors

Andra Noormägi¹, Tatjana Golubeva¹, Elina Berntsson^{1

2}, Sebastian K T S Wärmländer², Vello Tõugu¹, Peep Palumaa¹

Affiliations

¹ Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia.
² Chemistry Section, Stockholm University, 10691 Stockholm, Sweden.

Abstract

Copper is an indispensable biometal, primarily serving as a redox-competent cofactor in numerous proteins. Apart from preformed copper-binding sites within the protein structures, small peptide motifs exist called ATCUN, which are composed of an N-terminal tripeptide XZH, able to bind Cu(II) ions in exchangeable form. These motifs are common for serum albumin, but they are also present in a wide range of proteins and peptides. These proteins and peptides can be involved in copper metabolism, and copper ions can affect their biological role. The distribution of copper between the ATCUN peptides, including truncated amyloid-β (Aβ) peptides Aβ4-42 and Aβ11-42, which may be involved in Alzheimer's disease pathogenesis, is mainly determined by their concentrations and relative Cu(II)-binding affinities. The Cu(II)-binding affinity (log K_d) of several ATCUN peptides, determined by different methods and authors, varies by more than three orders of magnitude. This variation may be attributed to the chemical properties of peptides but can also be influenced by the differences in methods and experimental conditions used for the determination of K_d. In the current study, we performed direct competition experiments between selected ATCUN peptides and HSA by using an LC-ICP MS-based approach. We demonstrated that ATCUN and truncated Aβ peptides Aβ4-16 and Aβ11-15 bind Cu(II) ions with an affinity similar to that for HSA. Our results demonstrate that ATCUN motifs cannot compete with excess HSA for the binding of Cu(II) ions in the blood and cerebrospinal fluid.