1. 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.
2. New caerin antibiotic peptides from the skin secretion of the Dainty Green Tree Frog Litoria gracilenta. Identification using positive and negative ion electrospray mass spectrometry
Micheal J Maclean, Craig S Brinkworth, Daniel Bilusich, John H Bowie, Jason R Doyle, Lyndon E Llewellyn, Michael J Tyler Toxicon. 2006 May;47(6):664-75. doi: 10.1016/j.toxicon.2006.01.019. Epub 2006 Mar 22.
The skin secretion of the Dainty Green Tree Frog Litoria gracilenta contains 16 peptides, which protect the animal from predators, both large and small. A combination of negative and positive ion electrospray mass spectrometry together with Lys-C enzymic digest and Edman sequencing identifies three new wide-spectrum caerin 1 antibiotics, namely Caerin 1.17 [GLFSVLGSVAKHLLPHVAPIIAEKL-NH2], Caerin 1.18 [GLFSVLGSVAKHLLPHVVPVIAEKL-NH2], and Caerin 1.19 [GLFKVLGSVAKHLLPHVAPIIAEKL-NH2], and a narrow spectrum antibiotic Caerin 3.5 [GLWEKVKEKANELVSGIVEGVK-NH2].
3. Activities of seasonably variable caerulein and rothein skin peptides from the tree frogs Litoria splendida and Litoria rothii
Patrick J Sherman, Rebecca J Jackway, Emily Nicholson, Ian F Musgrave, Pinmanee Boontheung, John H Bowie Toxicon. 2009 Nov;54(6):828-35. doi: 10.1016/j.toxicon.2009.06.009. Epub 2009 Jun 17.
Two species of tree frog of the genus Litoria, namely L. splendida and L. rothii have been reported to change the compositions of their host-defence skin peptide profiles in summer and winter. L. splendida produces the potent smooth muscle active caerulein [pEQDY(SO(3)H)TGWMDF-NH(2)] in summer, but in winter much of the caerulein is hydrolysed to the less active desulfated form; in addition, caerulein 1.2 [pEQDY(SO(3)H)TGWFDF-NH(2)] (which has only some 50% of the smooth muscle activity of caerulein) is released and acts via CCK2R. In contrast, Litoria rothii shows a most unexpected seasonal change of peptides. In summer it exudes caerulein together with a range of potent caerin antimicrobials and nNOS active peptides. In winter, none of the antibiotic or nNOS active caerin peptides are expressed. The major peptides produced by the skin glands in winter are caerulein 1.2 and rothein 1 (SVSNIPESIGF-OH). Like L. splendida, L. rothii has reduced the smooth muscle potency of caerulein by replacing it with caerulein 1.2. Rothein 1 is a lymphocyte proliferator acting via CCK2R. Activity testing and 2D NMR spectra of rothein 1 and some synthetic modifications indicate that both hydrophobic and hydrophilic interactions between rothein 1 and CCK2R are important.
