Purification and cDNA cloning of an insecticidal protein from the venom ofthe scorpion Orthochirus scrobiculosus

Injection of crude venom from the scorpion Orthochirus scrobiculosus into l arvae of Heliothis virescens (Lepidoptera: Noctuidae) caused trembling and uncoordinated movement before development of a progressive and prolonged fl accid paralysis. The isolation of the toxin (OsI-1) responsible for this ef fect of O. scrobiculosus venom is described. The molecular mass of OsI-1 to xin was 6994 Da, as determined by desorption mass spectroscopy. The complet e primary structure of OsI-1 was deduced from the sequence of cDNA clones o btained by rapid amplification of cDNA ends (RACE) PCR. Comparison of the d educed amino acid sequence of OsI-1 with those of other insecticidal scorpi on toxins indicates that it is a sodium (Na+) channel active depressant ins ect-selective toxin. The analysis of amino acid sequence of the toxin in co njunction with mass spectroscopy data indicates post-translational modifica tion in maturation with the removal of 3 C-terminal amino acids and amidati on of the C-terminus. (C) 1999 Elsevier Science Ltd All rights reserved.