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Appl. Environ. Microbiol., Aug 1996, 2845-2849, Vol 62, No. 8
MK Lee, TH You, BA Young, JA Cotrill, AP Valaitis and DH Dean
We have evaluated the binding of Bacillus thuringiensis Cry toxins to
aminopeptidase N (APN) purified from Lymantria dispar (gypsy moth) brush
border membrane vesicle (BBMV). CryIAc toxin bound strongly to APN, while
either the structurally related CryIAa and CryIAb toxins or CryIC, CryIIA,
and CryIIIA toxins showed weak binding to APN. An in vitro competition
binding study demonstrated that the binding of CryIAc to L. dispar BBMV was
inhibited by APN. Inhibition of short circuit current for CryIAc, measured
by voltage clamping of whole L. dispar midgut, was substantially reduced by
addition of phosphatidylinositol- specific phospholipase C, which is known
to release APN from the midgut membrane. In contrast, addition of
phosphatidylinositol-specific phospholipase C had only a marginal effect on
the inhibition of short circuit current for CryIAa. These data suggest that
APN is the major functional receptor for CryIAc in L. dispar BBMV. A ligand
blotting experiment demonstrated that CryIAc recognized a 120-kDa peptide
(APN), while CryIAa and CryIAb recognized a 210-kDa molecule in L. dispar
BBMV. In contrast, CryIAa and CryIAb bound to both the 120- and 210-kDa
molecules in Manduca sexta BBMV, while CryIAc recognized only the 120- kDa
peptide. The 120-kDa peptide (APN) in L. dispar BBMV reacted with soybean
agglutinin, indicating that N-acetylgalactosamine is a component of this
glycoprotein.
Copyright © 1996, American Society for Microbiology
Aminopeptidase N purified from gypsy moth brush border membrane vesicles is a specific receptor for Bacillus thuringiensis CryIAc toxin
Department of Biochemistry, Ohio State University, Columbus 43210, USA.
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