1. Differences in the skin peptides of the male and female Australian tree frog Litoria splendida. The discovery of the aquatic male sex pheromone splendipherin, together with phe8 caerulein and a new antibiotic peptide caerin 1.10
P A Wabnitz, J H Bowie, M J Tyler, J C Wallace, B P Smith Eur J Biochem. 2000 Jan;267(1):269-75. doi: 10.1046/j.1432-1327.2000.01010.x.
The skin secretions of female and male Litoria splendida have been monitored monthly over a three-year period using HPLC and electrospray mass spectrometry. Two minor peptides are present only in the skin secretion of the male. The first of these is the female-attracting aquatic male sex pheromone that we have named splendipherin, a 25 amino acid peptide (GLVSSIGKALGGLLADVVKSKGQPA-OH). This pheromone constitutes about 1% of the total skin peptides during the breeding season (January to March), dropping to about 0.1% during the period June to November. Splendipherin attracts the female in water at a concentration of 10-11-10-9 M, and is species specific. The second peptide is a wide-spectrum antibiotic of the caerin 1 group, a 25 residue peptide (GLLSVLGSVAKHVLPHVVPVIAEKL-NH2) named caerin 1.10. The neuropeptides of L. splendida are also seasonally variable, the change identical for both the female and male. During the period October to March, the sole neuropeptide present in skin secretions is caerulein [pEQDY(SO3)TGWMDF-NH2]; this is active on smooth muscle and is also an analgaesic. During the southern winter (June to September), more than half of the caerulein is hydrolysed to [pEQDYTGWMDF-NH2], a peptide that shows no smooth muscle activity. In place of caerulein, a new peptide, Phe8 caerulein [pEQDY(SO3)TGWFDF-NH2], becomes a major component of the skin secretion. Perhaps this seasonal change is involved in thermoregulation, that is, with the initiation and maintenance of the inactive (hibernation) phase of the animal.
2. The rothein peptides from the skin secretion of Roth's tree frog Litoria rothii. Sequence determination using positive and negative ion electrospray mass spectrometry
Craig S Brinkworth, John H Bowie, Daniel Bilusich, Michael J Tyler Rapid Commun Mass Spectrom. 2005;19(18):2716-24. doi: 10.1002/rcm.2098.
The secretion from the dorsal glands of the frog Litoria rothii contains a series of new peptides including rothein 1 (SVSNIPESIGF-OH, a neuropeptide which contracts smooth muscle), a number of inactive rothein 2 and 3 peptides (e.g. rothein 2.1, AGGLDDLLEPVLNSADNLVHGL-OH), and a new proline rich peptide, named rothein 4.1 (AEILFGDVRPPWMPPPIFPEMP-OH), which shows neither antimicrobial nor neuronal nitric oxide synthase (nNOS) activity. Two known neuropeptides of the caerulein family [e.g. caerulein, pEQDY(SO3)TGWMDF-NH2] together with a series of known caerin 1 antibiotic and nNOS-inhibiting peptides (e.g. caerin 1.1, GLLSVLGSVAKHVLPHVVPVIAEHL-NH2) were also identified. Positive ion electrospray mass spectrometry (ES-MS) was used as the primary method to investigate the sequences of the new peptides. Negative ion ES-MS was used to fill in any gaps in the positive ion data and, finally, Edman automated sequencing was used to differentiate between Leu and Ile and to confirm the sequences determined by mass spectrometry.
3. The solution structure of frenatin 3, a neuronal nitric oxide synthase inhibitor from the giant tree frog, Litoria infrafrenata
Craig S Brinkworth, John A Carver, Kate L Wegener, Jason Doyle, Lyndon E Llewellyn, John H Bowie Biopolymers. 2003 Oct;70(3):424-34. doi: 10.1002/bip.10524.
The peptide frenatin 3 is a major component of the skin secretion of the Australian giant tree frog, Litoria infrafrenata. Frenatin 3 is 22 amino acids in length, and shows neither antimicrobial nor anticancer activity. It inhibits the production of nitric oxide by the enzyme neuronal nitric oxide synthase at a micromolar concentration by binding to its regulatory protein, Ca2+ calmodulin, a protein known to recognize and bind amphipathic alpha-helices. The solution structure of frenatin 3 has been investigated using NMR spectroscopy and restrained molecular dynamics calculations. In trifluoroethanol/water mixtures, the peptide forms an amphipathic alpha-helix over residues 1-14 while the C-terminal eight residues are more flexible and less structured. The flexible region may be responsible for the lack of antimicrobial activity. In water, frenatin 3 exhibits some alpha-helical character in its N-terminal region.
