A comparison of the positive- and negative-ion mass spectra of bio-active peptides from the dorsal secretion of the Australian red tree frog, Litoria rubella.

The collision-induced tandem mass spectral data for MH+ and [M-H]- ions from six bio-active peptides from Litoria rubella are compared. Backbone cleavages of [M-H]- ions provide sequencing information for five of the peptides [e.g. Phe Pro Trp Leu (NH2) and pGlu Phe Pro Trp Leu (NH2)] and in these cases, the negative-ion spectra are as informative as the positive-ion spectra. Side-chain cleavages are also noted in these spectra. For example, (i) when Trp is present, the loss of C9H7N (129 u) competes with the backbone cleavages, and (ii) the [M-H]- ion of Ile Glu Phe Phe Thr (NH2) undergoes facile side-chain fragmentation [loss of H2O (from Glu) and MeCHO (from Thr)], but does not form any conventional backbone-cleavage ions.

New caerin antibacterial peptides from the skin glands of the Australian tree frog Litoria xanthomera. Part 2. Sequence determination using mass spectrometry and associated techniques.

Mass spectrometric sequencing, enzymic digestion and Edman degradation provide the structures of the two antimicrobial peptides from the skin glands of the Australian tree frog Litoria xanthomera as:- Gly Leu Phe Ser Val Leu Gly Ala Val Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.6), and Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Ala Pro Val Ile Ala Glu Lys Leu (NH2) (caerin 1.7).

The application of mass spectrometry to the study of evolutionary trends in amphibians.

The glandular secretions of the skin of Litoria rubella specimens collected from five locations on the eastern seaboard of Queensland (Australia) contain the three tryptophyllin peptides Phe Pro Trp Leu (NH2), Phe Pro Trp Pro (NH2) and Phe Pro Phe Pro Trp Leu (NH2). The relative proportions of these peptides in the glandular secretion are associated with geographic location, i.e. Phe Pro Trp Pro (NH2) is a minor component of the peptide mixture in frogs from southern Queensland, but becomes significantly more abundant as the location becomes more northerly. This trend indicates an evolutionary change in the animal, but for what reason, and over what timescale is not known at this time.

A simple method for differentiating Leu and Ile in peptides. The negative-ion mass spectra of [M-H]- ions of phenylthiohydantoin Leu and Ile.

Phenylthiohydantoin (PTH) amino acid derivatives are formed during sequential Edman degradation of peptides and proteins. Isomeric Leu and Ile (which differ only in respectively having iso-butyl and sec-butyl chains, and are often difficult to distinguish by conventional mass spectrometric techniques) may be readily identified by the characteristic decompositions of the [M-H]- ions of their PTH derivatives. The Leu spectrum shows major loss of propane, while that of the Ile derivative shows elimination of both methane and ethane. This method may be used routinely with 10 microgram quantities of peptide material.

New antibiotic caerin 1 peptides from the skin secretion of the Australian tree frog Litoria chloris. Comparison of the activities of the caerin 1 peptides from the genus Litoria.

The skin glands of the tree frog Litoria chloris contain a variety of peptides including four antibacterial peptides of the caerin 1 family. Two of these, caerins 1.6 and 1.7, are also present in the related species Litoria xanthomera. The other two peptides, caerins 1.8 and 1.9, are new. Their sequences are: GLFKVLGSVAKHLLPHVVPVIAEKL-NH2 [Caerin 1.8] and GLFGVLGSIAKHVLPHVVPVIAEKL-NH2 [Caerin 1.9]. Comparison of the skin peptide profiles of L. chloris and L. xanthomera confirms that these species are more closely related to each other than to any other species of the genus Litoria that we have studied. A comparison is made of the antibiotic activities of nine members of the caerin 1 family of peptides isolated from tree frogs of the genus Litoria.

New caerin antibacterial peptides from the skin glands of the Australian tree frog Litoria xanthomera.

The secretion of the skin glands of the 'orange-thighed frog' Litoria xanthomera contains seven peptides. One of these is the know hypotensive peptide caerulein. Two new peptides, caerin 1.6 [GLFSVLGAVAKHVLPHVVPVIAEKL(NH2)], and caerin 1.7 [GLFKVLGSVAKHLLPHVAPVIAEKL(NH2)] show antibacterial properties. Two other peptides lack the first two amino acid residues of caerins 1.6 and 1.7 and show no antibacterial activity. The identification of the peptides in Litoria xanthomera confirms that this species is related to Litoria caerula, Litoria gilleni and Litoria splendida but not as closely as those three species are related to each other.

The maculatin peptides from the skin glands of the tree frog Litoria genimaculata: a comparison of the structures and antibacterial activities of maculatin 1.1 and caerin 1.1.

Six peptides have been isolated and characterized from the dorsal glands of the tree frog Litoria genimaculata. One of these is the known hypotensive peptide caerulein; the others have been named maculatins. The amino acid sequences of the maculatin peptides have been determined using a combination of fast atom bombardment mass spectrometry and automated Edman sequencing. Four of the maculatin peptides show antibiotic activity, with maculatin 1.1 [GLFGVLAKVAAHVVPAIAEHF(NH2)] showing the most pronounced activity, particularly against gram-positive organisms. Maculatin 1.1 resembles the known caerin 1 antibiotic peptides, except that four of the central amino acid residues (of the caerin 1 system) are missing in maculatin 1.1. A comparison of the antibiotic activity of maculatin 1.1 with those of caerin 1.1 is reported.

New caerin 1 antibiotic peptides from the skin secretion of the Australian tree frog Litoria chloris. Part 2. Sequence determination using electrospray mass spectrometry.

Electrospray mass spectrometry and automated Edman sequencing provides the structures of two new caerin 1 antimicrobial peptides from the skin glands of the Australian tree frog Litoria chloris. These are: caerin 1.8 Gly Leu Phe Lys Val Leu Gly Ser Val Ala Lys His Leu Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2), and caerin 1.9, Gly Leu Phe Gly Val Leu Gly Ser Ile Ala Lys His Val Leu Pro His Val Val Pro Val Ile Ala Glu Lys Leu (NH2).