OCCURRENCE OF A COMMON BINDING-SITE IN MAMESTRA-BRASSICAE, PHTHORIMAEA-OPERCULELLA, AND SPODOPTERA-EXIGUA FOR THE INSECTICIDAL CRYSTAL PROTEINS CRYIA FROM BACILLUS-THURINGIENSIS
B. Escriche et al., OCCURRENCE OF A COMMON BINDING-SITE IN MAMESTRA-BRASSICAE, PHTHORIMAEA-OPERCULELLA, AND SPODOPTERA-EXIGUA FOR THE INSECTICIDAL CRYSTAL PROTEINS CRYIA FROM BACILLUS-THURINGIENSIS, Insect biochemistry and molecular biology, 27(7), 1997, pp. 651-656
Specific binding to midgut membrane proteins is required for the toxic
ity of insecticidal crystal proteins (ICP) from Bacillus thuringiensis
, A direct relationship between toxicity and binding has been proposed
, It has been hypothesized that sharing of a single receptor by more t
han one ICP could lead to the occurrence of multiple resistance in the
event of an alteration in the common receptor, Binding of CryIA(a), C
ryIA(b) and CryIA(c), three structurally related ICPs, has been studie
d in Phthorimaea operculella, Mamestra brassicae and Spodoptera exigua
using brush border membrane vesicles (BBMV) from the midgut tissue, U
sing iodinated CryIA(b), the three insects showed similar results: one
binding site for CryIA(b), which is shared with CryIA(a) and CryIA(c)
, The binding site concentrations obtained for CryIA(b) in P, opercule
lla, M, brassicae and S, exigua were 5.1, 16.3 and 2.2 pmol/mg vesicle
protein, respectively, In the same way, dissociation constants were 3
.8, 5.3 and 0.7 nM, Data show that binding for an ICP does not directl
y imply toxicity. The occurrence of a common receptor for the CryIA su
bgroup of ICPs in P, operculella, M, brassicae and S, exigua might the
oretically discourage the use of combinations of these ICPs in integra
ted pest management programmes, (C) 1997 Elsevier Science Ltd.