title: Analysis of the disulfide linkage pattern in circulin A and B, HIV-inhibitory macrocyclic peptides.
abstract: Circulin A and B are members of a family of macrocyclic peptides, originally isolated from the tropical tree Chassalia parvifolia, that have been shown to display anti-HIV activity. Complete structural elucidation of these highly constrained peptides was difficult due to their cyclic amide backbone and the presence of six disulfide-linked cysteines. In the present study, the disulfide pairing motif of circulin A and circulin B was determined. Since the circulins were resistant to enzymatic proteolysis, cysteine residue pairings were identified by analysis of the complex mixture of cleavage products that resulted from partial acid hydrolysis of the native peptides. Combined utilization of HPLC, fast atom bombardment mass spectrometry and peptide recognition software ("F-MASS" and "F-LINK" programs) were employed to identify the cleavage products. Thus, we were able to unambiguously identify the disulfide linkage pattern in circulin A and circulin B as Cys1-Cys4, Cys2-Cys5 and Cys3-Cys6, where the numbers on the cystine residues refer to their respective order in the peptides.
authors.affiliation: Laboratory of Analytical Chemistry, NIDDK, NIH, Bethesda, Maryland 20892-0805, USA.
authors.forename: R
authors.initials: R
authors.lastname: Derua
authors.forename: K R
authors.initials: KR
authors.lastname: Gustafson
authors.forename: L K
authors.initials: LK
authors.lastname: Pannell
mesh_terms: D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D047169:Cyclotides; D004220:Disulfides; D006678:HIV / Q000187:drug effects*; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal; D012984:Software; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014197:Trees
chemical_list: D000998:Antiviral Agents; D047169:Cyclotides; D004220:Disulfides; D010456:Peptides, Cyclic; C091930:kalata B1; C102385:circulin B; C102384:circulin A