Cry1A toxins of Bacillus thuringiensis bind specifically to a region adjacent to the membrane-proximal extracellular domain of BT-R(1) in Manduca sexta: involvement of a cadherin in the entomopathogenicity of Bacillus thuringiensis.
Many subspecies of the soil bacterium Bacillus thuringiensis produce various parasporal crystal proteins, also known as Cry toxins, that exhibit insecticidal activity upon binding to specific receptors in the midgut of susceptible insects. One such receptor, BT-R(1) (210 kDa), is a cadherin located in the midgut epithelium of the tobacco hornworm, Manduca sexta. It has a high binding affinity (K(d) approximately 1nM) for the Cry1A toxins of B. thuringiensis. Truncation analysis of BT-R(1) revealed that the only fragment capable of binding the Cry1A toxins of B. thuringiensis was a contiguous 169-amino acid sequence adjacent to the membrane-proximal extracellular domain. The purified toxin-binding fragment acted as an antagonist to Cry1Ab toxin by blocking the binding of toxin to the tobacco hornworm midgut and inhibiting insecticidal action. Exogenous Cry1Ab toxin bound to intact COS-7 cells expressing BT-R(1) cDNA, subsequently killing the cells. Recruitment of BT-R(1) by B. thuringiensis indicates that the bacterium interacts with a specific cell adhesion molecule during its pathogenesis. Apparently, Cry toxins, like other bacterial toxins, attack epithelial barriers by targeting cell adhesion molecules within susceptible insect hosts.
Dorsch
J A
JA
Center for Biotechnology and Bioinformatics, The University of Texas at Dallas, P.O. Box 830688, FO31, Richardson, TX 75083-0688, USA.
Candas
M
M
Griko
N B
NB
Maaty
W S A
WS
Midboe
E G
EG
Vadlamudi
R K
RK
Bulla
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D001665:Binding Sites; D019556:COS Cells; D015820:Cadherins / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004731:Endotoxins / Q000378:metabolism*; D006460:Hemolysin Proteins; D019476:Insect Proteins; D007814:Larva; D018402:Manduca; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D014162:Transfection
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D015820:Cadherins; C095416:Cry toxin receptors; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; D011956:Receptors, Cell Surface; C030956:insecticidal crystal protein, Bacillus Thuringiensis