ABSTRACT
Three potent insecticidal peptide toxins were purified from the venom of the primitive weaving spider, Diguetia canities. The toxins share significant homology (> 40%) in their amino acid sequences and are of related size (masses of 6371-7080 Da). In lepidopteran larvae, the toxins cause a progressive spastic paralysis, with 50% paralytic doses (PD50S) ranging from 0.38 to 3.18 nmol/g, suggesting them to be among the most potent insecticidal compounds yet described from arthropod venoms. The most potent of these toxins, DTX9.2, was cloned using a reverse transcription-polymerase chain reaction (RT-PCR). The cDNA encodes a 94 amino acid precursor which is processed to the active 56 amino acid peptide by removal of a signal and propeptide sequence. The gene encoding DTX9.2 was isolated and characterized. The transcriptional unit spans 5.5 kilobases and is segregated into five exons. DNA sequences upstream from the first exon contain a TATA box and two palindromic sequences (one with homology to a CAAT consensus) which together may constitute a functional promoter. The highly segmented gene structure observed for this small peptide suggests that a mechanism such as exon shuffling may have played a role in the evolution of this toxin family.
Subject(s)
Insecticides/chemistry , Peptides/genetics , Spider Venoms/genetics , Amino Acid Sequence , Animals , Base Sequence , Cloning, Molecular , DNA , Male , Mice , Molecular Sequence Data , Peptides/chemistry , Spider Venoms/chemistry , Spider Venoms/pharmacology , SpidersABSTRACT
A continuing investigation of the umbellifer Lomatium dissectum has resulted in the isolation of a known flavonoid [1] and three coumarin glycosides [2-4], two of which are previously unreported. One of these new compounds [4] contains apiose, a sugar uncommon in the coumarins. The ichthyotoxicity of the plant extracts has been traced to the tetronic acids isolated earlier in this study.
