title: Histidine-containing host-defence skin peptides of anurans bind Cu2+. An electrospray ionisation mass spectrometry and computational modelling study.
abstract: Anuran peptides which contain His, including caerin 1.8 (GLFKVLGSVAKHLLPHVVPVIAEKL-NH(2)), caerin 1.2 (GLLGVLGSVAKHVLPHVVPVIAEHL-NH(2)), Ala(15) maculatin 1.1 (GLFGVLAKVAAHVVAIEHF-NH(2)), fallaxidin 4.1 (GLLSFLPKVIGHLIHPPS-OH), riparin 5.1 (IVSYPDDAGEHAHKMG-NH(2)) and signiferin 2.1 (IIGHLIKTALGMLGL-NH(2)), all form MMet(2+) and (M + Met(2+)-2H(+))(2+) cluster ions (where Met is Cu, Mg and Zn) following electrospray ionisation (ESI) in a Waters QTOF 2 mass spectrometer. Peaks due to Cu(II) complexes are always the most abundant relative to other metal complexes. Information concerning metal(2+) connectivity in a complex has been obtained (at least in part) using b and y fragmentation data from ESI collision-induced dissociation tandem mass spectrometry (CID MS/MS). Theoretical calculations, using AMBER version 10, show that MCu(2+) complexes with the membrane active caerin 1.8, Ala(15) maculatin 1.1 and fallaxidin 4.1 are four-coordinate and approximating square planar, with ligands including His and Lys, together with the carbonyl oxygens of particular backbone amide groups. When binding can occur through two His, or one His and one Lys, the His/Lys ligand structure is the more stable for the studied systems. The three-dimensional (3D) structures of the complexes are always different from the previously determined structures of the uncomplexed model peptides (using 2D nuclear magnetic resonance (NMR) spectroscopy in membrane-mimicking solvents like trifluoroethanol/water).
authors.affiliation: Department of Chemistry, The University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Tianfang
authors.initials: T
authors.lastname: Wang
authors.forename: Hayley J
authors.initials: HJ
authors.lastname: Andreazza
authors.forename: Tara L
authors.initials: TL
authors.lastname: Pukala
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Sherman
authors.forename: Antonio N
authors.initials: AN
authors.lastname: Calabrese
authors.forename: John H
authors.initials: JH
authors.lastname: Bowie
mesh_terms: D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism*; D001001:Anura / Q000378:metabolism*; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D052978:Disk Diffusion Antimicrobial Tests; D006639:Histidine / Q000737:chemistry / Q000378:metabolism*; D019216:Metals, Heavy; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; D019216:Metals, Heavy; D006639:Histidine; D003300:Copper