title: Primary and 3-D modelled structures of two cyclotides from Viola odorata.
abstract: Two polypeptides named vodo M and vodo N, both of 29 amino acids, have been isolated from Viola odorata L. (Violaceae) using ion exchange chromatography and reversed phase HPLC. The sequences were determined by automated Edman degradation, quantitative amino acid analysis, and mass spectrometry (MS). Using MS, it was established that vodo M (cyclo-SWPVCTRNGAPICGESCFTGKCYTVQCSC) and vodo N (cyclo-SWPVCYRNGLPVCGETCTLGKCYTAGCSC) form a head-to-tail cyclic backbone and that six cysteine residues are involved in three disulphide bonds. Their origin, sequences, and cyclic nature suggest that these peptides belong to the family of cyclic plant peptides, called cyclotides. The three-dimensional structures of vodo M and vodo N were modelled by homology, using the experimentally determined structure of the cyclotide kalata B1 as the template. The images of vodo M and vodo N show amphipathic structures with considerable surface hydrophobicity for a protein modelled in a polar environment.
authors.affiliation: Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Centre, Box 574, SE-751 23 Uppsala, Sweden.
authors.forename: Erika
authors.initials: E
authors.lastname: Svangård
authors.forename: Ulf
authors.initials: U
authors.lastname: Göransson
authors.forename: Derek
authors.initials: D
authors.lastname: Smith
authors.forename: Chandra
authors.initials: C
authors.lastname: Verma
authors.forename: Anders
authors.initials: A
authors.lastname: Backlund
authors.forename: Lars
authors.initials: L
authors.lastname: Bohlin
authors.forename: Per
authors.initials: P
authors.lastname: Claeson
mesh_terms: D000595:Amino Acid Sequence; D003198:Computer Simulation; D047169:Cyclotides; D030562:Databases, Protein; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D011487:Protein Conformation; D019666:Rubiaceae / Q000737:chemistry; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein; D032413:Viola / Q000737:chemistry*
chemical_list: D047169:Cyclotides; D010456:Peptides, Cyclic; C091930:kalata B1