title: Conformational analysis of the broad-spectrum antibacterial peptide, ranatuerin-2CSa: identification of a full length helix-turn-helix motif.
abstract: Design of clinically valuable antibacterial agents based upon naturally occurring peptides requires the use of spectroscopic methods, particularly NMR, to determine the three-dimensional structure of the native peptide so that analogues with improved therapeutic properties can be made. Ranatuerin-2CSa (GILSSFKGVAKGVAKDLAG KLLETLKCKITGC), first isolated from skin secretions of the Cascades frog, Rana cascadae, represents a promising candidate for drug development. The peptide shows potent growth inhibitory activity against Escherichia coli (MIC=5 microM) and Staphylococcus aureus (MIC=10 microM) but displays haemolytic activity against human erythrocytes (LC(50)=160 microM). The solution structure of ranatuerin-2CSa was investigated by proton NMR spectroscopy and molecular modelling. In aqueous solution, the peptide lacks secondary structure but, in a 2,2,2-trifluoroethanol (TFE-d(3))-H(2)O solvent mixture, the structure is characterised by a full length helix-turn-helix conformation between residues I(2)-L(21), L(22)-L(25) and K(26)-T(30) respectively. This structural information will facilitate the design of novel therapeutic agents based upon the ranatuerin-2CSa structure with improved antimicrobial potencies but decreased cytolytic activities against mammalian cells.
authors.affiliation: UCD School of Biomolecular and Biomedical Science, UCD Centre for Synthesis and Chemical Biology, UCD Conway institute, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Anusha P
authors.initials: AP
authors.lastname: Subasinghage
authors.forename: J Michael
authors.initials: JM
authors.lastname: Conlon
authors.forename: Chandralal M
authors.initials: CM
authors.lastname: Hewage
mesh_terms: D000595:Amino Acid Sequence; D029845:Amphibian Proteins / Q000737:chemistry* / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides; D004926:Escherichia coli / Q000187:drug effects; D019077:Helix-Turn-Helix Motifs; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013211:Staphylococcus aureus / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D029845:Amphibian Proteins; D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D010455:Peptides; C121230:ranatuerin