Evidence of the involvement of E358, A498 and C571 of a new Cry1Ac delta-endotoxin of Bacillus thuringiensis in its high insecticidal activity against Ephestia kuehniella.
A new cry1Ac-type gene was cloned from Bacillus thuringiensis strain BLB1, sequenced and expressed. The deduced amino acid sequence of the polypeptide has a predicted molecular mass of 132.186 kDa. The amino acid sequence alignment of BLB1 Cry1Ac with those of the published ones showed that this is a new delta-endotoxin. When compared with Cry1Ac of Bacillus thuringiensis strain HD1, it was found that BLB1 Cry1Ac harbours three mutations: V358E localized in domain II and V498A and Y571C localized in domain III. When the BLB1 Cry1Ac toxin was expressed in an acrystalliferous strain of B. thuringiensis (HD1CryB), bipyramidal crystals were produced. The spore-crystal mixture of this recombinant strain was at least two-fold more active against larvae of the lepidopteran Ephestia kuehniella than that of the recombinant strain expressing Cry1Ac of HD1. The study of the structural effect of these mutations suggested that they may stabilize key regions involved in the binding of the domains II and III to insect receptors.
Saadaoui
Imen
I
Laboratory of Biopesticides, Centre of Biotechnology of Sfax, Sfax, Tunisia.
Miled
Nabil
N
Jaoua
Samir
S
D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D004731:Endotoxins / Q000737:chemistry* / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism*; D007915:Lepidoptera / Q000382:microbiology* / Q000502:physiology*; D008969:Molecular Sequence Data; D010572:Pest Control, Biological / Q000379:methods*; D013329:Structure-Activity Relationship
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis