Effects of Bacillus thuringiensis var.israelensis 20-kDa Protein on Production of the Bti 130-kDa Crystal Protein in Escherichia coli

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A 20-kDa protein of Bacillus thuringiensis var. israelensis (Bti) has been shown to be necessary for the efficient expression of the 27-kDa mosquitocidal protein gene in Escherichia coli. We have investigated the effects of this 20-kDa protein on the expression of two 130-kDa mosquitocidal protein genes (cryIV A, cryIV B) in E.coli by supplying the 20-kDa protein gene in trans. When a recombinant plasmid, pLH4BX, which was constructed to express cryIV A under the E.coli lac promoter on pUC19, coexisted with the 20-kDa protein gene, a striking increase in production of the fused CryIV A was detected. This was not accompanied by an increase in the amount of intracellular mRNA, suggesting that 20-kDa protein exerts a posttranscriptional effect. We conclude that the 20-kDa protein also stimulates the production of 130-kDa protein in E.Coli.