Translation of a stable mRNA fraction from sporulating cells of Bacillus thuringiensis in a cell-free system from Escherichia coli. Structural homologies between the native crystal protein and the products synthesized in vitro.

Stable messenger RNAs from sporulating cells of Bacillus thuringiensis were translated in vitro in cell free system from E. coli. The mRNA fraction used was extracted from cells treated at t4 of sporulation time with rifampicin for 10 minutes at 30degreesC. This stable-mRNA enriched fraction directed the synthesis of polypeptides showing a size distribution up to 40,000 daltons. Structural homologies between the in vitro products labeled with [3H]-valine and the native crystal protein labeled with [14C]-valine were shown by ion-exchange chromatography after CNBr treatment and by ion-exchange chromatography after digestion of the CNBr-peptides with pepsin. Specific antibodies obtained against the CNBr-peptides of the native crystal protein gave a positive reaction with the in vitro products. SDS-gel electrophoresis confirmed the structural similarities between the two types of immuno-precipitates. It was concluded that the stable-mRNA fraction used directed the synthesis of at least parts of the crystal polypeptide chain. Furthermore, the higher stability of the sporulation phase mRNAs compared to that of the vegetative phase species deduced from previous in vivo experiments was supported by the results obtained in vitro.