physalaemin and hylambatin

Theoretical conformational analysis of N-terminal fragments of the title peptides has been carried out using the potential energy calculations. The number of conformational states for each fragment is very limited, and they are easily interconverted. Since these fragments cannot form alpha-helises, it is unlikely that upon binding of tachikinins to their receptors, their N-terminal fragments could overcome the hydrophobic barrier of the cell membrane's lipid belayer.

Topics: Amino Acid Sequence; Lipid Bilayers; Molecular Sequence Data; Physalaemin; Protein Conformation; Substance P; Tachykinins

Hylambatin (Hyl), a dodecapeptide isolated from the skin of the African frog, Hylambates maculatus, belongs to the family of tachykinin or physalaemin-like peptides. Hylambatin and its 12 fragments were tested in the guinea-pig ileum preparation for contractile activities. All fragments except 3 had contractile activities. The C-terminal fragment as short as the octapeptide sequence was at least as active as the parent molecules. The heptapeptide fragment (Hyl6-12) and the hexapeptide fragment (Hyl7-12) were less active and the C-terminal pentapeptide fragment (Hyl8-12) and the N-terminal hexapeptide fragment (Hyl1-6) were much less active. The N-terminal pentapeptide fragment (Hyl1-5) and the N-terminal fragment from which the N-terminal Asp or Asp-Pro residues were removed (Hyl2-6, Hyl3-6), were inactive at doses used.

Topics: Animals; Guinea Pigs; Ileum; In Vitro Techniques; Kinins; Muscle Contraction; Muscle, Smooth; Peptide Fragments; Physalaemin; Structure-Activity Relationship

Topics: Animals; Galanin; Guinea Pigs; Indicators and Reagents; Muscle Contraction; Peptides; Physalaemin; Structure-Activity Relationship

Hylambatin, a novel tachykinin endecapeptide isolated from the skin of the African frog Hylambates maculatus, must be ascribed to the physalaemin subfamily. It differs structurally from all other known tachykinins mainly in having a methionine residue replacing the usual leucine residue at position 2 from the C-terminus. In parallel bioassay on a number of in-vitro and in-vivo test objects, hylambatin and physalaemin were nearly indistinguishable from each other, with few moderate quantitative differences.

Topics: Animals; Blood Pressure; Colon; Female; Guinea Pigs; Ileum; In Vitro Techniques; Kinins; Muscle Contraction; Muscle, Smooth; Physalaemin; Rabbits; Rats; Salivation; Urinary Bladder; Uterus

Hylambatin is the first example of a tachykinin which possesses a methionyl methionine residue at the C-terminus, rather than the C-terminal tripeptide -Gly-Leu-Met-NH2 which hitherto has been a characteristic feature of all members of the tachykinin family. The effect of hylambatin on the secretion of glucoregulatory hormones was examined in the rat. Hylambatin, injected intravenously in graded doses 10 and 30 min before blood collection, significantly increased both plasma glucose and plasma insulin, whereas the secretion of glucagon was not affected. This profile of action is different from that of kassinin or substance P. Should hylambatin, like other neuropeptides, be present in mammalian tissue, it may have a role in the regulation of carbohydrate metabolism.

Topics: Animals; Blood Glucose; Glucagon; Insulin; Insulin Secretion; Kinins; Male; Nerve Tissue Proteins; Physalaemin; Rats; Rats, Inbred F344; Tachykinins