Identification of Bombyx mori Midgut Receptor for Bacinus thuringiensis Insecticidal CryIA ( a

As part of a study of the mechanism by which BaciUus thun'ngiensis nsecticidal crystal protein acts, a Bombyx mori receptor to the CryIA(a) toxin specific for lepidopterans was examined. Histolegical examination showed that the toxin acted on the brush-border membrane of the midgut columllar cells and broke its info}ding structure, causing cell lysis. The membrane vesicles were purified, and a 175kDa protein binding the toxin was found that acco"nted for some O.O15 % of membrane proteins. The protein, designated BtR175, was a glycopretein that reacted with collcanayalin A. Anti-BtR antibodies inhibited the binding of toxin te membrane yesicles in vitro and decreased the effect of the toxin to silkworms in vivo. BtR175, although found in the gllt, was not fo"nd in fat bodies, integument, or silk glands. These resu]ts indicated that BtR175 was the receptor protein for the insecticidal toxin. Proteins (137 and 107 kDa) binding the CryIA(a) texin also were follnd in the gllt membralles of 11enebrio m ritor larvae, a coleopteran not