Coordination Environment of Cu(II) Ions Bound to N-Terminal Peptide Fragments of Angiogenin Protein

Abstract

Angiogenin (Ang) is a potent angiogenic factor, strongly overexpressed in patients affected by different types of cancers. The specific Ang cellular receptors have not been identified, but it is known that Ang–actin interaction induces changes both in the cell cytoskeleton and in the extracellular matrix. Most in vitro studies use the recombinant form (r-Ang) instead of the form that is normally present in vivo (“wild-type”, wt-Ang). The first residue of r-Ang is a methionine, with a free amino group, whereas wt-Ang has a glutamic acid, whose amino group spontaneously cyclizes in the pyro-glutamate form. The Ang biological activity is influenced by copper ions. To elucidate the role of such a free amino group on the protein–copper binding, we scrutinized the copper(II) complexes with the peptide fragments Ang(1–17) and AcAng(1–17), which encompass the sequence 1–17 of angiogenin (QDNSRYTHFLTQHYDAK-NH2), with free amino and acetylated N-terminus, respectively. Potentiometric, ultraviolet-visible (UV-vis), nuclear magnetic resonance (NMR) and circular dichroism (CD) studies demonstrate that the two peptides show a different metal coordination environment. Confocal microscopy imaging of neuroblastoma cells with the actin staining supports the spectroscopic results, with the finding of different responses in the cytoskeleton organization upon the interaction, in the presence or not of copper ions, with the free amino and the acetylated N-terminus peptides.

From Peptide Fragments to Whole Protein: Copper(II) Load and Coordination Features of IAPP

“…These values are indicative of the involvement of three nitrogen atoms and are related with either a square‐pyramidal or a tetrahedral distorted square‐planar coordination geometry . Furthermore, these EPR parameters are very similar to those reported for the analogous species having a {NH 2 , N − , N Im, CO} metal coordination mode …”

Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry, Speciation and Coordination of the Metal Complexes

“…[88] Nuclear magnetic resonance (NMR) spectroscopy:N MR experiments were carried out on aB ruker Ascend TM 400 MHz spectrometer (Bruker,B illerica, MA, USA) equipped with a5mm automated tuning and matching broad band probe (BBFO) with z-gradients, as previously described. [89][90][91][92] NMR spectra were recorded by using 1mm solution of the appropriate peptide in 90: Simulation details:T he solution NMR structure of r-IAPP(1-37) (pdb code 2kj7) [93] and r-IAPP(1-37;R18 H) (pdb code 2kb8) [73,74] were considered as initial coordinates. Those were solvated in a truncated octahedron box with 16 775 and 16 783 water molecules, respectively,n eutralized by 4c hloride ions, energy minimized and equilibrated through 2nso fM Ds imulations.…”

Gold Nanoparticles Functionalized with Angiogenin for Wound Care Application

“…In this regard, it has been demonstrated that copper ions are able to stimulate endothelial cell migration and neovascularization in avascular rabbit corneas while its depletion, by Cu-chelators, such as penicillamine and trientine, in vivo, prevents the vessels formation [ 14 , 15 ]. Such an intersection between copper and angiogenesis supports the critical role of the metal in pathological and physiological angiogenic processes, such as wound repair where a higher concentration of copper ions (~30 μM) has been detected with respect to the peri-wound areas [ 16 , 17 ]. Hence, the local modulation of copper pro-angiogenic effect provides a promising strategy to enhance tissue repair and regeneration.…”