title: CD and NMR structural characterization of ceratotoxins, natural peptides with antimicrobial activity.
abstract: Antibacterial properties of the secretion from the female reproductive accessory glands of medfly Ceratitis capitata are mostly ascribed to the presence of two peptides, ceratotoxin A and B, which exhibit a strong activity against gram-positive and gram-negative bacterial strains, and show sequence and function homology with cecropins, melittin, and magainins. CD experiments performed in different solvents indicate the presence of a significant content of helical structures in organic solvent. Two-dimensional nmr results for ceratotoxin A in methanol show a helical behavior for the 8-25 region of the peptide. A ramachandran classification of each residue for the structures obtained from distance geometry calculations lead to the definition of four structural families in which the central segment 10-19 is always helical and differences refer to residues 8-9 and 19-23. A sequence analysis of the two ceratotoxins and a systematic search on the protein data bank revealed the occurrence of a KX-hydrophobic-hydrophobic-P motif that seems to be important for helix stabilization.
authors.affiliation: TECHNOBIOCHIP, Milano, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Ragona
authors.forename: H
authors.initials: H
authors.lastname: Molinari
authors.forename: L
authors.initials: L
authors.lastname: Zetta
authors.forename: R
authors.initials: R
authors.lastname: Longhi
authors.forename: D
authors.initials: D
authors.lastname: Marchini
authors.forename: R
authors.initials: R
authors.lastname: Dallai
authors.forename: L F
authors.initials: LF
authors.lastname: Bernini
authors.forename: L
authors.initials: L
authors.lastname: Lozzi
authors.forename: M
authors.initials: M
authors.lastname: Scarselli
authors.forename: N
authors.initials: N
authors.lastname: Niccolai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry*; D001704:Biopolymers / Q000737:chemistry; D002942:Circular Dichroism; D004175:Diptera; D005260:Female; D007301:Insect Hormones / Q000737:chemistry* / Q000235:genetics; D019476:Insect Proteins; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry / Q000235:genetics; D017433:Protein Structure, Secondary; D012996:Solutions; D013816:Thermodynamics
chemical_list: D000890:Anti-Infective Agents; D001704:Biopolymers; D007301:Insect Hormones; D019476:Insect Proteins; D010455:Peptides; D012996:Solutions; C082689:ceratotoxin A protein, Ceratitis capitata; C082690:ceratotoxin B protein, Ceratitis capitata