No abstract

LyeTx I, an antimicrobial peptide isolated from the venom of Lycosa erythrognatha, known as wolf spider, has been synthesised and its structural profile studied by using the CD and NMR techniques. LyeTx I has shown to be active against bacteria (Escherichia coli and Staphylococcus aureus) and fungi (Candida krusei and Cryptococcus neoformans) and able to alter the permeabilisation of L: -alpha-phosphatidylcholine-liposomes (POPC) in a dose-dependent manner. In POPC containing cholesterol or ergosterol, permeabilisation has either decreased about five times or remained unchanged, respectively. These results, along with the observed low haemolytic activity, indicated that antimicrobial membranes, rather than vertebrate membranes seem to be the preferential targets. However, the complexity of biological membranes compared to liposomes must be taken in account. Besides, other membrane components, such as proteins and even specific lipids, cannot be discarded to be important to the preferential action of the LyeTx I to the tested microorganisms. The secondary structure of LyeTx I shows a small random-coil region at the N-terminus followed by an alpha-helix that reached the amidated C-terminus, which might favour the peptide-membrane interaction. The high activity against bacteria together with the moderate activity against fungi and the low haemolytic activity have indicated LyeTx I as a good prototype for developing new antibiotic peptides.

Sea anemones are known to contain a wide diversity of biologically active peptides, mostly unexplored according to recent peptidomic and transcriptomic studies. In the present work, the neurotoxic fractions from the exudates of Stichodactyla helianthus and Bunodosoma granulifera were analyzed by reversed-phase chromatography and mass spectrometry. The first peptide fingerprints of these sea anemones were assessed, revealing the largest number of peptide components (156) so far found in sea anemone species, as well as the richer peptide diversity of B. granulifera in relation to S. helianthus. The transcriptomic analysis of B. granulifera, performed by massive cDNA sequencing with 454 pyrosequencing approach allowed the discovery of five new APETx-like peptides (U-AITX-Bg1a-e - including the full sequences of their precursors for four of them), which together with type 1 sea anemone sodium channel toxins constitute a very distinguishable feature of studied sea anemone species belonging to genus Bunodosoma. The molecular modeling of these new APETx-like peptides showed a distribution of positively charged and aromatic residues in putative contact surfaces as observed in other animal toxins. On the other hand, they also showed variable electrostatic potentials, thus suggesting a docking onto their targeted channels in different spatial orientations. Moreover several crab paralyzing toxins (other than U-AITX-Bg1a-e), which induce a variety of symptoms in crabs, were isolated. Some of them presumably belong to new classes of crab-paralyzing peptide toxins, especially those with molecular masses below 2kDa, which represent the smallest peptide toxins found in sea anemones.

No abstract

No abstract

No abstract

No abstract

No abstract