title: Conformational heterogeneity in polypeptide cardiac stimulants from sea anemones.
abstract: High-resolution 1H NMR spectra at 300 MHz of the polypeptide cardiac stimulants anthopleurin-A and Anemonia sulcata toxin II reveal conformational heterogeneity in both molecules. The two conformations, manifest in a number of split 1H resonances, are in slow exchange over a wide range of pH and temperature. Heterogeneity affects a region of these molecules containing the structurally and functionally important Asp residues. By comparison with a homologous polypeptide Anemonia sulcata toxin I, which does not show this type of heterogeneity, it is suggested that the heterogeneity may originate in cis-trans isomerism of the Gly-40 to Pro-41 peptide bond.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002316:Cardiotonic Agents / Q000302:isolation & purification*; D003063:Cnidaria; D003064:Cnidarian Venoms / Q000302:isolation & purification; D036341:Intercellular Signaling Peptides and Proteins; D009682:Magnetic Resonance Spectroscopy; D010455:Peptides / Q000302:isolation & purification*; D011487:Protein Conformation; D012615:Sea Anemones; D013329:Structure-Activity Relationship
chemical_list: D002316:Cardiotonic Agents; D003064:Cnidarian Venoms; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C036310:toxin I (Anemonia sulcata); C028800:toxin II (Anemonia sulcata); C012746:anthopleurin-A