Exploration of receptor binding of Bacillus thuringiensis toxins

• Main Authors: In-Seok Kwak, Hong Lu, Donald H Dean
• Format: Article
• Language: English
• Published: Instituto Oswaldo Cruz, Ministério da Saúde 1995-02-01
• Series: Memórias do Instituto Oswaldo Cruz.
• Subjects: ion channel toxin; biological insecticide
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0074-02761995000100017

Wild type and mutant toxins of Bacillus thuringiensis delta-endotoxins were examined for their binding to midgut brush border membrane vesicles (BBMV). CryIAa, CryIAb, and CryIAc were examined for their binding to Gypsy moth (Lymantria dispar) BBMV. The binding of CryIAa and CryIAc was directly correlated with their toxicity, while CryIAb was observed to have lower binding than expected from its toxicity. The latter observation confirms the observation of Wolfersberger (1990). The "rule" of reciprocity of binding and toxicity is apparently obeyed by CryIAa and CryIAc, but broken by CryIAb on L. dispar. Alanine substitutions were made in several positions of the putative loops of CryIAa to test the hypothesis that the loops are intimately involved in binding to the receptor. The mutant toxins showed minor shifts in heterologous binding to Bombyx mori BBMV, but not enough to conclude that the residues chosen play critical roles in receptor binding.