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Cover Picture: Isolation, Amino Acid Sequence and Biological Activities of Novel Long-Chain Polyamine-Associated Peptide Toxins from the Sponge Axinyssa aculeata (ChemBioChem 14/2011)
The cover picture shows a schematic structure of Aculeine A, a novel peptide toxin modified with long-chain polyamines (LCPAs), and the marine sponge Axynissa acureata, from which the peptide was isolated. In the background is an underwater photograph taken off Iriomote Island, Okinawa (Japan) where this sponge is found. Aculeines, which induce convulsions in mice upon intra-cerebroventricular injection and disrupt neuronal membrane integrity in electrophysiological assays, are 44-residue ribosomal peptides whose amino acid sequence contains a cysteine-knot motif. The N-terminal residue is a highly modified tryptophan that is associated with polypropanamine oligomers of up to 15 repetitive units. The highly modified N-terminal structure is an unprecedented structural feature among naturally occurring peptides. For more information, see the paper by R. Sakai et al. on p. 2191 ff.