Open AccessElucidation of a Copper Binding Site in Proinsulin C-peptide and Its Implications for Metal-Modulated Activity
Author(s) -
Michael J. Stevenson,
Samuel E. Janisse,
Lizhi Tao,
Ryan L. Neil,
Quang D. Pham,
R. David Britt,
Marie C. Heffern
Publication year - 2020
Publication title -
inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 233
eISSN - 1520-510X
pISSN - 0020-1669
DOI - 10.1021/acs.inorgchem.0c01212
Subject(s) - peptide , chemistry , proinsulin , binding site , random coil , metal , peptide sequence , combinatorial chemistry , biochemistry , stereochemistry , circular dichroism , insulin , biology , endocrinology , organic chemistry , gene
The connecting peptide (C-peptide) is a hormone with promising health benefits in ameliorating diabetes-related complications, yet mechanisms remain elusive. Emerging studies point to a possible dependence of peptide activity on bioavailable metals, particularly Cu(II) and Zn(II). However, little is known about the chemical nature of the interactions, hindering advances in its therapeutic applications. This work uncovers the Cu(II)-binding site in C-peptide that may be key to understanding its metal-dependent function. A combination of spectroscopic studies reveal that Cu(II) and Zn(II) bind to C-peptide at specific residues in the N-terminal region of the peptide and that Cu(II) is able to displace Zn(II) for C-peptide binding. The data point to a Cu(II)-binding site consisting of 1N3O square-planar coordination that is entropically driven. Furthermore, the entire random coil peptide sequence is needed for specific metal binding as mutations and truncations reshuffle the coordinating residues. These results expand our understanding of how metals influence hormone activity and facilitate the discovery and validation of both new and established paradigms in peptide biology.