Bradykinin-related peptides from Phyllomedusa hypochondrialis azurea: Mass spectrometric structural characterisation and cloning of precursor cDNAs.
Amphibian skin secretions contain a plethora of bioactive compounds, many of which are understood to act to deter ingestion by predators. Bradykinins in particular are constitutively expressed in many amphibian skin secretions, mediating a variety of effects including hyperalgesia and contraction of gastric smooth muscle. Using a variety of proteomic techniques (high-performance liquid chromatography (HPLC) separation, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS), and quadrupole time-of-flight tandem mass spectrometry (Q-TOF-MS/MS)) the current study identified 13 bradykinin-like peptides in the skin secretions of Phyllomedusa hypochondrialis azurea, including several new C-terminally extended isoforms (VPPGFTPFRLT, VHypPGFTPFRQT) and a novel phyllokinin-like peptide (RPPGFTPFRVY). Identification of the cDNA sequences encoding these peptides led to the deduction that the peptides were derived from differential post-translational processing and modification of five different precursors. Such an event emphasises the metabolic efficiency of peptide production in amphibian venom, with multiple products perhaps selective to different receptors in a variety of predators generated from a single precursor. An unusual modification was also recognised in the present study, with several bradykinin-like peptides featuring hydroxyprolination of the first proline residue rather than the commonly targeted second. This alteration may be mediated by the structural organisation of N-terminal amino acids prior to precursor processing.
Thompson
Alan Hunter
AH
Institute of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, UK.
Bjourson
Anthony John
AJ
Shaw
Chris
C
McClean
Stephen
S
D000595:Amino Acid Sequence; D000818:Animals; D001001:Anura / Q000378:metabolism*; D001920:Bradykinin / Q000032:analysis / Q000737:chemistry* / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary / Q000235:genetics*; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D020539:Sequence Analysis, Protein / Q000379:methods*; D012867:Skin / Q000378:metabolism*
D018076:DNA, Complementary; D020033:Protein Isoforms; D001920:Bradykinin