ReviewHost-defense peptides of Australian anurans. Part 2. Structure, activity, mechanism of action, and evolutionary significance
Highlights
► Use of e.g. NMR and QCM-D methods to determine how membrane-active peptides destroy cell membranes. ► Anuran peptides which form complexes with Ca2+ CaM resulting in deactivation of nNOS. ► Divergent structures of neuropeptides including smooth-muscle agents, opioids and immunomodulators. ► cDNA sequences of pre-pro-peptides from dorsal glands of anurans provide evolutionary data.
Introduction
During the past 25 years we have isolated and identified peptides from the secretions of skin glands of some 40 species of Australian frogs and toads (anurans) from the genera Crinia, Cyclorana, Limnodynastes, Litoria and Uperoleia: this work has been previously reviewed in this Journal to 2004 [4]. Secretions are obtained using electrical stimulation of the glands on the dorsal skin, a technique which does not harm the anurans [118]. We have identified membrane active peptides, hormones, neuropeptides (including smooth muscle active peptides, opioids and immunomodulators), nNOS inhibitors and a male sex pheromone [4], [17], [123]. Reviews of bio-active peptides from anurans elsewhere are also available [8], [10], [39], [50], [52], [90], [97]. This review of peptides from Australian anurans covers the years 2004–2011.
Section snippets
Structure determination of peptides
The original review [4] had a major section on structure determination of peptides which included discussions of nuclear magnetic resonance spectroscopy and mass spectrometry, both positive and negative ion. That is not repeated here, but a recent advance in mass spectrometry is mentioned. Positive ion mass spectrometry remains the major mass spectroscopic method for sequence determination of peptides [11] but there have been recent advances in negative ion mass spectrometry of
Membrane-active peptides
An updated list of membrane active peptides is shown in Table 1. Most of the work since 2004 devoted to the peptides listed in Table 1 has involved either activities or mechanisms of peptide penetration of the cell membrane. Work prior to 2004 on antibacterial, anticancer, antifungal and antiviral activities, together with membrane penetration mechanisms were described in the earlier review [4]. Here, the subjects of (i) activity and (ii) membrane penetration mechanisms will be dealt separately.
Neuropeptides
The pharmacology of those amphibian peptides classified loosely as “neuropeptides” has been covered in detail in Erspamer's review in 1994 [50]. The majority of Australian frogs, froglets and toads have at least one such host-defense peptide in their glandular secretions: the sequences of these peptides are summarized in Table 2. Active peptides classified as tryptophyllins (and their analogs) will be discussed separately later.
A significant number of the compounds shown in Table 2 have one or
Neuronal nitric oxide inhibitors
Llewellyn and Doyle of the Australian Institute of Marine Science, as part of the then AIMS neuropeptide testing programme, showed that the anuran peptides listed in Table 4 inhibited the formation of the ubiquitous chemical messenger nitric oxide from neuronal nitric oxide synthase at micromolar concentrations. There were also many amphibian peptides which showed no inhibition of nNOS, for example the majority of those listed in Table 3, Table 5.
The experimental method involves the measurement
Peptides whose activities have not been determined
It is surprising that there are so many peptides, often peptides produced in significant amounts in glandular secretions, which are inactive in our testing regime. It seems unlikely that a frog will devote energy to produce a major peptide which has no specific purpose in the anuran integument. The “inactive” members of the tryptophyllin and rubellidin families of peptides are examples (Table 3) as are those peptides listed in Table 5. The small peptides isolated from species of the Cyclorana
Pheromones from anurans
A review of pheromone type molecules, including peptides, of aquatic animals and amphibians is available [39]. Pheromones were covered in the previous review [4]. It has now been shown that the male sex pheromone of L. splendida, splendipherin [GLVSSIGKALGGLLADVVKSKGQPA(OH)], moves across the surface of water via a surface tension gradient [94].
Mature adult hybrid females were produced in captivity from a single mating of a female L. splendida and a male L. caerulea. The hybrid females were not
Peptide profiling
The use of HPLC peptide profiles of glandular secretions to differentiate between anurans (frogs and toads) of different genera and of different species within the same genus has been detailed in previous reviews [4], [73] as has the application of peptide profiling to indicate different populations of frogs within a particular species [73]. For example peptide profiling was used to indicate that (i) there are two populations of Litoria ewingi in South Australia [73], and (ii) the frog
Conclusions
The peptide compositions of the skin glandular secretions of some 40 of the 230 species of Australian anurans have been studied. Although many questions have been raised and answered as a result of this research, some questions remain unanswered.
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It is now clear that the skin peptide profile of some (but not all) frogs of the genus Litoria may change with the seasons; sometimes the nature of the antibiotic peptides change from winter to summer, other times the “neuropeptide” content may change
Acknowledgements
We thank the Australian Research Council for financing our research on anuran peptides, and for partially funding the NMR spectrometers, mass spectrometers and supercomputers used in this research. We thank our colleagues, the post-doctoral fellows and many graduate students who were involved with the projects carried out in Adelaide and/or Melbourne: their names are shown as authors of the publications listed in the reference section of this review. MJT thanks the many volunteers who assisted
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2023, Bioorganic and Medicinal Chemistry LettersAntibacterial activity of a scorpion-derived peptide and its derivatives in vitro and in vivo
2020, ToxiconCitation Excerpt :The AMP MK049518 (FLGLLGSVLGSVLPSIFK) was identified by the transcriptome analysis of the venom gland of the crab-scorpion Didymocentrus krausi without functional study (Rojas-Azofeifa et al., 2019). MK049518 demonstrated a high identity to the AMP Maculatin 1.4 (Bowie et al., 2012), which indicated that the peptide may have antimicrobial activity. In this study, we found that the peptide could only inhibit the growth of the tested Gram-positive bacteria (Table 2), which is consistent with previous studies that many natural AMPs have a limited spectrum or a low activity against bacteria (Fox, 2013; Wang and Wang, 2016).
Glu residues of βDELSEED-motif are essential for peptide binding in Escherichia coli ATP synthase
2018, International Journal of Biological MacromoleculesCitation Excerpt :Antimicrobial peptides affect bacteria, fungi, viruses, parasites, and cancer cells [63,64]. Programmed cell death via a mitochondrial pathway by selective inhibition of ATP synthase [65–68] and synergistic effects of antimicrobial peptides among α-helical peptides have also been observed [69]. Given results of the current study, Glu residues of the βDELSEED-motif are essential for the binding and interaction of peptides with ATP synthase.