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Toxin-Binding Proteins from Midgut Epithelium Membranes of Anopheles stephensi Larvae

M. A. Dronina1, L. P. Revina1, L. I. Kostina1, L. A. Ganushkina2, I. A. Zalunin1*, and G. G. Chestukhina1

1Scientific Research Institute for Genetics and Selection of Industrial Microorganisms, 1-yi Dorozhnyi Proezd 1, 117545 Moscow, Russia; fax: (7-495) 315-0501; E-mail: zalunin@genetika.ru

2Sechenov Moscow Medicine Academy, Martsinovsky Institute of Medical Parasitology and Tropical Medicine, ul. Bolshaya Pirogovskaya 2, Korpus 3, 119992 Moscow, Russia

* To whom correspondence should be addressed.

Received April 13, 2005; Revision received June 17, 2005
Proteins of 65 and 57 kD were isolated from the apical membranes of midgut epithelium of Anopheles stephensi larvae by affinity chromatography. These proteins can specifically bind endotoxin Cry11A and activate toxin Cry4B (Cry4B-tox) under conditions of ligand blotting, and both Cry proteins compete for this binding. At least in the case of Cry4B-tox, the binding with 65 and 57 kD proteins is reversible. The ability of the products of limited proteolysis of Cry11A and Cry4B to bind the 65 and 57 kD proteins correlates with their toxicity to A. stephensi larva. The N-terminal amino acid sequence of the 57 kD protein is unique and absent in the NCBI GenBank. The proteins of 65 and 57 kD share most of the properties studied with Aedes aegypti toxin-binding proteins. It is possible that they altogether represent a novel class (or classes) of delta-endotoxin receptors.
KEY WORDS: delta-endotoxins, Bacillus thuringiensis, toxin-binding proteins, Anopheles stephensi

DOI: 10.1134/S0006297906020039