Dynamic Stereoselection of Peptide Helicates and Their Selective Labeling of DNA Replication Foci in Cells**

Abstract

Peptide engineering has been extremely successful in creating new structures with defined properties and functions. Although generally overlooked in this context, coordination chemistry offers an additional set of interactions that opens unexplored design opportunities for developing complex molecular structures. With this in mind, we report the development of new artificial peptide ligands that fold into chiral and discrete supramolecular helicates in the presence of labile metal ions such as Fe(II) and Co(II). By selecting appropriate heterochiral β-turn promoting sequences, we can encode the stereoselective folding of the peptide ligand, and define the physicochemical properties of their corresponding metal complexes. The study of these metallopeptides by CD and NMR spectroscopy, combined with computational methods allowed us to identify and determine the structure of two isochiral ΛΛ-helicates, folded as topological isomers. We also show that these new peptide helicates, dynamically selected in the presence of labile Co(II) ions, can be locked as kinetically-inert species by in situ oxidation to Co(III). Finally, in addition to the in vitro characterization of their selective binding to three-way DNA, cell microscopy experiments demonstrated that a rhodamine-labeled Fe(II) helicate was internalized and selectively stains DNA replication factories in functional cells. File list (2) download file view on ChemRxiv Manusrcipt_ChemRxiv.pdf (1.76 MiB) download file view on ChemRxiv Supporting Information.pdf (7.91 MiB)

Cavity-Containing [Fe2L3]4+ Helicates: An Examination of Host-Guest Chemistry and Cytotoxicity

“…The biological properties of the Fe(II) and Ru(II) systems were poor but the more robust Co(III) helicates were shown to bind to and condense DNA and in addition displayed good anticancer activity ( Crlikova et al, 2020 ). Di(2,2′-bipyridine) ligands ( Glasson et al, 2008 ; Glasson et al, 2011a ; Glasson et al, 2011b ) have also been used to generate [M 2 L 3 ] 4+ triple-stranded helicates and recently Vázquez and co-workers have examined the DNA binding and cytotoxicity of some peptide linked [M 2 L 3 ] 4+ helicates [where M = Fe(II) or Co(III)] ( Gamba et al, 2014 ; Gómez-González et al, 2018 ; Gomez-Gonzalez et al, 2021 ).…”

Artificial Metal–Peptide Assemblies: Bioinspired Assembly of Peptides and Metals through Space and across Length Scales

“…Note that helicate MPA-12 had already shown the potential biological application in selectively labeling DNA replication foci in the nuclei. 97 MPA-16 with helically chiral channel exhibited remarkable recognition and binding of maltopentaose by virtue of its superior microenvironment. 108 We expect that artificial peptide-derived complexes are capable of exceptional affinities and selectivities for biomolecules.…”

“…For instance, a longer flexible ligand (L-9), which features six 2,2′-bipyridine (bpy) as chelators and two heterochiral (L-L-D configuration) tripeptide fragments with a Arg-Pro-Arg sequence as β-turns, can be precisely folded into chiral triple-stranded helicates (MPA-12) in the presence of configurationally labile metal ions such as Fe(II) or Co(II) (Figure 8C). 97 In this system, it allowed great freedom in the choice of the side-chain groups in the loops, as long as they maintained their relative chirality. As anticipated, the four charged arginine residues endow the helicates excellent solubility and thermodynamic stability in aqueous media.…”

“…(C) Self-assembly and representative structures of MPA-12 . (C) Reproduced with permission from ref . Copyright 2021 Wiley-VCH.…”

Supramolecular Cylinders Target Bulge Structures in the 5′ UTR of the RNA Genome of SARS‐CoV‐2 and Inhibit Viral Replication**

“…These helicate cylinders are currently the only metallosupramolecular architectures that have been demonstrated to thread through RNAbulge and junction structures,but there is ag rowing interest in metallo-supramolecular designs to bind nucleic acid structures. [53,54] While the SHAPE experiments provide further demonstrations of cylinder selectivity for junctions and bulges over other nucleic acid structures,an exciting possibility is that cylinders might also be able to bind host-cell RNAs tructures,m achinery on which the virus depends for replication, causing ad ual anti-proliferation effect. Ther esults herein suggest that nucleic acid binding metallo-supramolecular architectures,a nd the cylinder designs in particular, merit further exploration as anti-viral agents.…”