title: Peptide IC-20, encoded by skin kininogen-1 of the European yellow-bellied toad, Bombina variegata, antagonizes bradykinin-induced arterial smooth muscle relaxation.
abstract: OBJECTIVE
  The objectives were to determine if the skin secretion of the European yellow-bellied toad (Bombina variegata), in common with other related species, contains a bradykinin inhibitor peptide and to isolate and structurally characterize this peptide.
  
  
  METHODS
  Lyophilized skin secretion obtained from this toad was subjected to reverse phase HPLC fractionation with subsequent bioassay of fractions for antagonism of the bradykinin activity using an isolated rat tail artery smooth muscle preparation. Subsequently, the primary structure of the peptide was established by a combination of microsequencing, mass spectroscopy, and molecular cloning, following which a synthetic replicate was chemically synthesised for bioassay.
  
  
  RESULTS
  A single peptide of molecular mass 2300.92 Da was resolved in HPLC fractions of skin secretion and its primary structure determined as IYNAIWP-KH-NK-KPGLL-. Database interrogation with this sequence indicated that this peptide was encoded by skin kininogen-1 previously cloned from B. variegata. The blank cycles were occupied by cysteinyl (C) residues and the peptide was located toward the C-terminus of the skin kininogen, and flanked N-terminally by a classical -KR- propeptide convertase processing site. The peptide was named IC-20 in accordance (I = N-terminal isoleucine, C = C-terminal cysteine, 20 = number of residues). Like the natural peptide, its synthetic replicate displayed an antagonism of bradykinin-induced arterial smooth muscle relaxation.
  
  
  CONCLUSIONS
  IC-20 represents a novel bradykinin antagonizing peptide from amphibian skin secretions and is the third such peptide found to be co-encoded with bradykinins within skin kininogens.
authors.affiliation: School of Pharmacy, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK.
authors.forename: Mu
authors.initials: M
authors.lastname: Yang
authors.forename: Mei
authors.initials: M
authors.lastname: Zhou
authors.forename: Bing
authors.initials: B
authors.lastname: Bai
authors.forename: Chengbang
authors.initials: C
authors.lastname: Ma
authors.forename: Le
authors.initials: L
authors.lastname: Wei
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Tianbao
authors.initials: T
authors.lastname: Chen
authors.forename: Chris
authors.initials: C
authors.lastname: Shaw