title: Identification of insect-selective and mammal-selective toxins from Parabuthus leiosoma venom.
abstract: Venoms were collected from two scorpion species: Parabuthus leiosoma and Parabuthus pallidus from Kenya. Subcutaneous injection and oral toxicity tests of crude and pure fractions of scorpion venoms were done in Mus musculus (mice), Chilo partellus and Busseola fusca. The highest activity against C. partellus was found in P. leiosoma venom (LC(50) 0.689 mg/50mg body weight). Bioassay-guided purification by a combination of cation-exchange (CE) and reverse-phase high-performance liquid chromatography (RP-HPLC) led to the isolation of three toxic peptides. A lepidopteran-selective toxin (P. leiosoma insect toxin, Plit) was isolated, and the partial N-terminal amino acid sequence (-KDGYPVDNANCKYE-) plus the molecular weight (6688.5 Da) determined. A peptide with significant insect toxicity coupled with mild effects on mice (P. leiosoma toxin, Plt) was isolated, and the partial N-terminal amino acid sequence (-LCEKFKVQRLVELNCVD-) plus the molecular weight (6742.5 Da) was determined. Another toxin with anti-mammalian activity (P. leisoma mammal-selective toxin, Plmt), and N-terminal partial amino acid sequence of ADVPGNYPLDKNGNRYY- plus a molecular weight of 7145.5 Da was also isolated. Comparison of the partial N-terminal amino acid sequences with other toxins revealed that Plit shows high homology to other known insect toxins. Similarly, Plmt shows high homology with several birtoxin-like anti-mammalian toxins. Plt does not exhibit homology with any known scorpion toxin with combined anti-insect and anti-mammalian activity.
authors.affiliation: Behavioural and Chemical Ecology Department, The International Center of insect Physiology and Ecology, PO Box 30772, Nairobi 00100, Kenya.
authors.forename: John B
authors.initials: JB
authors.lastname: Ochola
authors.forename: Wilber
authors.initials: W
authors.lastname: Lwande
authors.forename: Thuku
authors.initials: T
authors.lastname: Thiong'o
authors.forename: Lucie
authors.initials: L
authors.lastname: Rogo
authors.forename: Rafael
authors.initials: R
authors.lastname: Herrmann
authors.forename: Eric
authors.initials: E
authors.lastname: Schepers
authors.forename: Richard
authors.initials: R
authors.lastname: Bagine
authors.forename: Paul
authors.initials: P
authors.lastname: Mungai
authors.forename: Isaiah O
authors.initials: IO
authors.lastname: Ndiege
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007306:Insecticides / Q000737:chemistry / Q000302:isolation & purification*; D051379:Mice; D008969:Molecular Sequence Data; D012604:Scorpion Venoms / Q000737:chemistry* / Q000633:toxicity
chemical_list: D007306:Insecticides; D012604:Scorpion Venoms