title: African Viper Poly-His Tag Peptide Fragment Efficiently Binds Metal Ions and Is Folded into an α-Helical Structure.
abstract: Snake venoms are complex mixtures of toxic and often spectacularly biologically active components. Some African vipers contain polyhistidine and polyglycine peptides, which play a crucial role in the interaction with metal ions during the inhibition of snake metalloproteases. Polyhistidine peptide fragments, known as poly-His tags, play many important functions, e.g., in metal ion transport in bacterial chaperon proteins. In this paper, we report a detailed characterization of Cu(2+), Ni(2+), and Zn(2+) complexes with the EDDHHHHHHHHHG peptide fragment (pHG) derived from the venom of the rough scale bush viper (Atheris squamigera). In order to determine the thermodynamic properties, stoichiometry, binding sites, and structures of the metal-pHG complexes, we used a combination of experimental techniques (potentiometric titrations, electrospray ionization mass spectrometry, UV-vis spectroscopy, circular dichroism spectroscopy, and electron paramagnetic resonance spectroscopy) and extensive computational tools (molecular dynamics simulations and density functional theory calculations). The results showed that pHG has a high affinity toward metal ions. The numerous histidine residues located along this sequence are efficient metal ion chelators with high affinities toward Cu(2+), Ni(2+), and Zn(2+) ions. The formation of an α-helical structure induced by metal ion coordination and the occurrence of polymorphic binding states were observed. It is proposed that metal ions can "move along" the poly-His tag, which serves as a metal ion transport pathway. The coordination of Cu(2+), Ni(2+), and Zn(2+) ions to the histidine tag is very effective in comparison with other histidine-rich peptides. The stabilities of the metal-pHG complexes increase in the order Zn(2+) < Ni(2+)≪ Cu(2+).
authors.affiliation: †Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Watly
authors.forename: Eyal
authors.initials: E
authors.lastname: Simonovsky
authors.affiliation: †Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
authors.forename: Nuno
authors.initials: N
authors.lastname: Barbosa
authors.affiliation: ∥Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Spodzieja
authors.affiliation: †Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
authors.forename: Robert
authors.initials: R
authors.lastname: Wieczorek
authors.affiliation: ∥Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Rodziewicz-Motowidlo
authors.forename: Yifat
authors.initials: Y
authors.lastname: Miller
authors.affiliation: †Faculty of Chemistry, University of Wrocław, 50-383 Wrocław, Poland.
authors.forename: Henryk
authors.initials: H
authors.lastname: Kozlowski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006639:Histidine / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D019216:Metals, Heavy / Q000378:metabolism* / Q000494:pharmacology; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding / Q000187:drug effects; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014757:Viper Venoms / Q000737:chemistry; D017819:Viperidae
chemical_list: D007093:Imidazoles; D019216:Metals, Heavy; D010446:Peptide Fragments; D014757:Viper Venoms; C033223:polyhistidine; D006639:Histidine