CHARACTERIZATION OF ALPHA-NEUROTOXIN AND PHOSPHOLIPASE A(2) ACTIVITIES FROM MICRURUS VENOMS - DETERMINATION OF THE AMINO-ACID-SEQUENCE AND RECEPTOR-BINDING ABILITY OF THE MAJOR ALPHA-NEUROTOXIN FROM MICRURUS-NIGROCINCTUS-NIGROCINCTUS

New World elapids are coral snakes that belong to the genus Micrurus, and for which the venom biochemistry is mostly unknown. Analysis has b een difficult because the coral snakes produce small quantities of ven om. Clinical observations following bites show mainly neurotoxic effec ts. Experimentally, cardiotoxic, haemolytic and myotoxic activities ar e also reported. An experimental approach, using reverse-phase high-pe rformance liquid chromatography and specific assays for alpha-neurotox in and phospholipase Az activities, was conducted on milligram quantit ies of venoms from three Micrurus species from Costa Rica; M. nigrocin ctus nigrocinctus, M. alleni yatesi and M. multifasciatus. Neurotoxici ty was determined by competition binding experiments with the Torpedo marmorata acetylcholine receptor. Phospholipase A, activity was measur ed by fluorimetry using a pyrene lipid substrate. In this way, we puri fied and characterized seven alpha-neurotoxins, five phospholipases A( 2) and four toxin homologs. The amino acid sequence of the major alpha -neurotoxin from M. nigrocinctus nigrocinctus venom was fully determin ed and compared to Old Word representatives. Distance matrix data were generated to set up phylogeny relationships among elapid short-chain alpha-neurotoxins, which proved to be in accordance with the taxonomic classification and geographical distribution of snake species.