A glycine-leucine-rich peptide structurally related to the plasticins from skin secretions of the frog Leptodactylus laticeps (Leptodactylidae).
A glycine-leucine-rich peptide was isolated from norepinephrine-stimulated skin secretions of the Sante Fe frog Leptodactylus laticeps (Leptodactylidae) whose primary structure (Gly-Leu-Val-Asn-Gly-Leu-Leu-Ser-Ser-Val-Leu-Gly-Gly-Gly-Gln-Gly-Gly-Gly-Gly-Leu-Leu-Gly-Gly-Ile-Leu) contains the (GXXXG)(3) motif found in the plasticins, previously identified only in phyllomedusid frogs (Hylidae). Circular dichroism studies showed that the secondary structure of the peptide, termed plasticin-L1, was markedly solvent-dependent displaying a random coil conformation in water, a beta-sheet structure in methanol, and an alpha-helical conformation in 50% trifluoroethanol-water. A synthetic replicate of the peptide did not inhibit the growth of Escherichia coli or Staphylococcus aureus or lyse human erythrocytes at concentrations up to 500 microM. At relatively high concentrations (>or=1 microM), the peptide produced a significant (P<0.05), although modest (139% of basal rate at 3 microM), increase in the rate of glucose-induced release of insulin from rat clonal BRIN-BD11 beta cells without increasing the rate of release of lactate dehydrogenase. A peptide, termed ocellatin-L2 was also identified in the skin secretion that was identical to the previously described ocellatin-L1 except for the substitution Asn(23)-->Asp. Ocellatin-L2 was devoid of antimicrobial and hemolytic activity but also showed significant activity in stimulating insulin release from BRIN-BD11 cells (181% of basal rate at 3 microM).
Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates. jmconlon@uaeu.ac.ae
J Michael
JM
Conlon
Yasser H A
YH
Abdel-Wahab
Peter R
PR
Flatt
Jérôme
J
Leprince
Hubert
H
Vaudry
Thierry
T
Jouenne
Eric
E
Condamine
D000818:Animals; D001001:Anura; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects; D005136:Eye Proteins / Q000737:chemistry*; D005998:Glycine / Q000032:analysis*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007930:Leucine / Q000032:analysis*; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation; D012867:Skin / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects
D005136:Eye Proteins; D007328:Insulin; D009419:Nerve Tissue Proteins; D010455:Peptides; C076104:plasticin; D007930:Leucine; D005998:Glycine