BACILLUS-THURINGIENSIS DELTA-ENDOTOXIN BINDING-SITES IN 2 LEPIDOPTERA, WISEANA SPP AND EPIPHYAS-POSTVITTANA

Proteins from the midguts of the light-brown apple moth Epiphyas postv ittana (Walker) and the porina caterpillars Wiseana cervinata (Walker) , W. copularis (Meyrick), and IV. jocosa (Meyrick) which bind the Baci llus thuringiensis delta-endotoxin Cry1Ba were characterized using Cry 1Ba labeled with Bolton and Hunter reagent. A comparison of two iodine labeling techniques on the toxicity of B. thuringiensis delta-endotox ins showed that labeling using chloramine-T substantially decreased Cr y1Ba toxicity against the light-brown apple moth E. postvittana, where as labeling using the Bolton and Hunter reagent had no effect on the t oxicity of either Cry1Ac or Cry1Ba to this insect. The characteristics of Cry1Ac binding sites from E. postvittana midguts were determined b y competitive binding assays using toxin labeled with I-125 by both me thods. The difference in values of binding site characteristics found by the two methods was shown to be caused by modification of the toxin by the conditions of chloramine-T labeling. The relationship between number and affinity of the binding sites and the toxicity of the delta -endotoxins is discussed. (C) 1997 Academic Press.