A cDNA,library from the skin of Kuna temporaria has been screened using a cDNA fragment probe that encodes the signal peptide of the precursor of esculentin from the skin secretion of Rana esculentu. With this approach, the cDNAs encoding the precursors of three peptides were isolated. Subsequently, the peptides predicted from the sequence of the cloned cDNAs as well as several structurally related peptides could be isolated from the skin secretion of R. temporuria. These peptides, which were named temporins, have a length of 10-13 residues and show some sequence similarity to hemolytic peptides Natural and synthetic temporins have antibacterial activity against gram-positive bacteria, but they are not hemolytic. Temporins are the smallest antibacterial peptides hitherto found in nature.

A multimeric protein that behaves functionally as an authentic ferritin has been isolated from the Gram-positive bacterium Listeria innocua. The purified protein has a molecular mass of about 240,000 Da and is composed of a single type of subunit (18,000 Da). L. innocua ferritin is able to oxidize and sequester about 500 iron atoms inside the protein cage. The primary structure reveals a high similarity to the DNA-binding proteins designated Dps. Among the proven ferritins, the most similar sequences are those of mammalian L chains that appear to share with L. innocua ferritin the negatively charged amino acids corresponding to the iron nucleation site. In L. innocua ferritin, an additional aspartyl residue may provide a strong complexing capacity that renders the iron oxidation and incorporation processes extremely efficient. This study provides the first experimental evidence for the existence of a non-heme bacterial ferritin that is related to Dps proteins, a finding that lends support to the recent suggestion of a common evolutionary origin of these two protein families.

Deltorphins are endogenous linear heptapeptides, isolated from skin extracts of frogs belonging to the genus PhyUomedusa, that have a higher affinity and selectivity for 6 opioid binding sites than any other natural compound known. Two deltorphins with the sequence Tyr-Ala-Phe-Asp(or Glu)-Val-Val-Gly-NH2 have been isolated from skin extracts of PhyUomedusa bicolor. The alanine in position 2 is in the D configuration. These peptides, deltorphins I and II, show an even higher affinity for 6 receptors than the previously characterized deltorphin, which contains D-methionine as the second amino acid. These peptides show some similarity to another constituent of Phylomedusa skin, dermorphin, which is highly selective for ,u-opioid receptors. These peptides all have the N-terminal sequence Tyr-D-Xaa-Phe, where D-Xaa is either D-alanine or D-methionine. While this structure seems to be capable of activating both pA and 6 opioid receptors, differences in the C-terminal regions of these peptides are probably responsible for the observed high receptor selectivity of dermorphin and deltorphin.The endogenous opioid ligands isolated from vertebrate brain show little selectivity toward the different types of opioid receptors. Peptides isolated from amphibian skin appear to be more selective. In 1981 Montecucchi et al. (1) extracted from the skin of the Argentinian frog Phyllomedusa sauvagei a heptapeptide named dermorphin, which preferentially binds to A-type opioid receptors (2). By recombinant DNA techniques, it was demonstrated that dermorphin, like numerous other peptides, is derived in multiple copies from larger precursors. In addition, from inspection of the sequence of one of the cloned cDNAs for these precursors, the existence of another heptapeptide with an N-terminal region similar to that of dermorphin was predicted (3). We recently succeeded in isolating small quantities of this peptide from the skin ofP. sauvagei and named it deltorphin, because of its high affinity and selectivity for the 8 opioid binding site (4). Both dermorphin and deltorphin contain a D amino acid (D-alanine and D-methionine, respectively) as the second amino acid. In the cloned cDNAs, codons for the corresponding L amino acids-i.e., GCG for alanine and ATG for methionine-were found at these positions. This characteristic suggested that the processing of these peptides includes a reaction whereby an L amino acid residue is converted to its D isomer within peptide linkage (3). Here we describe the isolation of two other heptapeptides from the skin of Phyllomedusa bicolor, which show an affinity and selectivity for 8 opioid receptors several times higher than that of deltorphin and the cyclic enkephalin derivative enkephalin (DPDPE, where D-Pen is D-penicillamine) (5). Once again, these peptides contain a D-alanine residue in the second position and share with dermorphin and deltorphin the N-terminal sequence Tyr-D-Xaa-Phe. We refer to these peptides, which differ by the presence of an aspartic or glutamic residue in position 4,...

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