| Popis: |
The collective evidence from several laboratories demonstrates that foreign genes from both prokaryotes and eukaryotes, can be expressed in B. subtilis if the heterologous gene is placed under the control of Bacillus promoters and ribosome binding sites. The nucleotide sequences of several Bacillus promoters are very similar to the consensus E. coli promoter sequence at both the -10 and -35 recognition sites. In spite of this apparent similarity, E. coli promoters appear to be poorly recognized in vitro by B. subtilis RNA polymerase35. Thus, a barrier to heterologous (E. coli) gene expression in B. subtilis may reside at the transcriptional level. In addition, there appears to be a barrier at the level of translation. Rabinowitz and co-workers have shown that ribosomes from gram-positive bacteria, including B. subtilis, are relatively inactive in the in vitro translation of mRNA gram-negative species. This appears to be due to an inability of ribosomes from gram-positive bacteria to use the relatively weak ribosome binding sites that commonly occur in RNA from gram-negative bacteria. |
