The Cry3A protein expressed in these transgenic potato cultivars is
identical to that found in nature and in commercial Bt spray
formulations. Cry proteins, of which Cry3A is only one, act by
selectively binding to specific sites localized on the lining of
the midgut of susceptible insect species. Following binding, pores
are formed that disrupt midgut ion flow causing gut paralysis and
eventual death due to bacterial sepsis. Cry3A is insecticidal only
when eaten by the larvae of coleopteran insects such as Colorado
potato beetle and its specificity of action is directly
attributable to the presence of specific binding sites in the
target insects. There are no binding sites for delta-endotoxins of
B. thuringiensis on the surface of mammalian intestinal cells,
therefore, livestock animals and humans are not susceptible to
these proteins.
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