Binding of phylogenetically distant Bacillus thuringiensis cry toxins to a Bombyx mori aminopeptidase N suggests importance of Cry toxin's conserved structure in receptor binding.
We investigated the binding proteins for three Cry toxins, Cry1Aa, Cry1Ac, and the phylogenetically distant Cry9Da, in the midgut cell membrane of the silkworm. In a ligand blot experiment, Cry1Ac and Cry9Da bound to the same 120-kDa aminopeptidase N (APN) as Cry1Aa. A competition experiment with the ligand blot indicated that the three toxins share the same binding site on several proteins. The values of the dissociation constants of the three Cry toxins and 120-kDa APN are as low as the case of other Cry toxins and receptors. These results suggest that distantly related Cry toxins bind to the same site on the same proteins, especially with APN. We propose that the conserved structure in these three toxins includes the receptor-binding site.
Shinkawa
A
A
Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
Yaoi
K
K
Kadotani
T
T
Imamura
M
M
Koizumi
N
N
Iwahana
H
H
Sato
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D012831:Bombyx / Q000201:enzymology*; D018826:CD13 Antigens / Q000378:metabolism*; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism*; D006460:Hemolysin Proteins; D007422:Intestines / Q000201:enzymology; D008024:Ligands; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D008024:Ligands; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D018826:CD13 Antigens