Bradykinin‐related peptides from Phyllomedusa hypochondrialis azurea: mass spectrometric structural characterisation and cloning of precursor cDNAs

Abstract

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.

Mass spectrometric study of bradykinin‐related peptides (BRPs) from the skin secretion of Russian ranid frogs

“…It was first isolated and described by Schroeder and coworkers in 1997, and it has not been found in any frog skin secretions until now. Its presence verifies the hypothesis of Chen et al and Thompson et al that the main function of BRPs involves resistance to possible predators, including birds in the case of the common frog, R. temporaria , which live mostly on the land.…”

“…Bradykinin and BRPs were reported to provoke the pharyngeal reflex that prevents swallowing of a prey and intensifies pain . The isolation of BRPs similar to that of fish and snake from amphibian skin secretions has led some investigators to suggest that the primary target of amphibian BRPs involves the corresponding receptors in the possible predators . However, the definite mechanism of the action of BRPs remains uncertain.…”

“…The major known BRPs from the abovementioned frogs were identified by cloning of bradykinin precursor cDNAs from amphibian skins. In some cases cloning of the BRP precursors was accompanied by a targeted search for structural analogues of the already known BRPs . Usually mass spectral analysis was applied only to those separated fractions of the skin secretion which demonstrated some biological activity.…”

Identification of bradykinin: related peptides from Phyllomedusa nordestina skin secretion using electrospray ionization tandem mass spectrometry after a single-step liquid chromatography

“…Moreover, some amphibian secretions contain a number of small proteins and a large number of peptide components whose biological functions are still undetermined. Several peptides from skin secretions of amphibians, more particularly tree-frogs, have been purified in recent years, including antimicrobial peptides, bradykinin related peptides and one bradykinin-potentiating peptide (BPP) (5)(6)(7)(8)(9).…”

The Enigma of Double-stranded RNA (dsRNA) Associated with Mushroom Virus X (MVX)

“…C: Screening of known and unknown fractions of Pseudomonas syringae toxins/lipodepsipeptides. Thompson et al (2006). The instrument was operated in positive ion "V" optics mode with a spray voltage of 3.5 kV and a cone voltage of 100 V and for further MS/MS studies the selected precursor ion was fragmented using collision energy of 30 eV.…”