title: The identification and structure-activity relations of a cardioactive FMRFamide-related peptide from the blue crab Callinectes sapidus.
abstract: The pericardial organs and thoracic ganglia of the blue crab Callinectes sapidus were resected and extracted. The extracts were fractionated by HPLC and the fractions analyzed by a radioimmunoassay (RIA) to FMRFamide. Multiple peaks of immunoreactivity were present and one of these, upon fast atom bombardment mass spectrometry (FAB-ms) and microsequencing, yielded the sequence GYNRSFLRFamide. The amount of this peptide in each crab is between 7 and 13 pmol. Several incomplete sequences were also characterized, suggesting a precursor with multiple copies of peptides related to GYNRSFLRFamide might occur. The peptide caused a dose-dependent increase in heart rate; threshold was 10 to 30 nM, and the EC50 was 323 +/- 62 nM. A structure-activity study of GYNRSFLRFamide on the crab heart suggests that, for full potency, a peptide should be at least a heptapeptide with the sequence XXZFLRFamide, where X is any amino acid and Z is either asparagine or serine.
authors.affiliation: Whitney Laboratory, University of Florida, St. Augustine 32086-8632.
authors.forename: K G
authors.initials: KG
authors.lastname: Krajniak
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003386:Brachyura / Q000737:chemistry*; D002316:Cardiotonic Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D019835:FMRFamide; D006339:Heart Rate / Q000187:drug effects; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D002316:Cardiotonic Agents; D009479:Neuropeptides; D019835:FMRFamide