Structural and functional studies of latrodectin from the venom of black widow spider (Latrodectus tredecimguttatus).

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Spider venoms are a rich source of potential probes for ion channels and receptors in nerve cells (Kawai and Nakajima, 1993). From a biochemical point of view, the study of the molecular composition of spider venoms, is not easy because a large number of venom glands are necessary from animals which are generally small, and frequently, difficult to collect in large number. To avoid these limitations, we have been recently induced to use a molecular biology approach, to study spider venoms. In fact, cloning and expression of cDNAs offers an alternative to secure sufficient material to the purpose of detecting molecules having pharmacological activities. In the venom of the Mediterranean black widow spider (Latrodectus tredecimguttatus) we developed the initial idea to sequence and clone the most interesting neurotoxin, named alpha-latrotoxin. The potentialities of this project were based on a limited amino acid sequence available for the toxin (Pescatori et al., 1995). In fact, alpha-latrotoxin was considered to be a single-polypeptide toxin that exerts its neurotoxic action, by dramatically affecting synaptic vesicles exocytosis at the nerve endings (Grasso, 1988). The finding that this toxin could stimulate neurosecretion has been of great interest in neurobiology and the possibility of developing its use, as a pharmacological tool for the study of neurotransmitter release at various nerve terminals, has been greatly developed, afterwards. At nerve endings, the toxin stimulates and supports secretion even in the absence of external calcium, thus offering a great variation, not even considered before, of experimental conditions to test. Furthermore, alpha-latrotoxin binds with a high-affinity to receptor which is localised exclusively at the presynaptic plasma membrane (Petrenko et al., 1990). The molecular organisation of presynaptic structures has been derived by the development of functional analysis on toxin-receptor interactions (Petrenko, 1993; O’Connor et al., 1993).KeywordsVenom GlandGland ExtractImmunoaffinity ColumnSpider VenomImmunoaffinity PurificationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.