Mutagenesis study to ameliorate the bacterial expression of phosphoprotein P of vesicular stomatitis virus

The phosphoprotein gene of vesicular stomatitis virus, a Rhabdovirus, has been inserted into bacterial expression plasmids containing the Escherichia coli tac promoter and ribosome binding site (RBS). A low level of expression of the protein was detected. Sequence analysis showed the presence of 15 nucleotides in the spacer region i.e., between the Shine-Dalgarno sequence and ATG. Alteration of the distance and the sequence in the spacer region by oligonucleotide-directed mutagenesis revealed a correlation among the expression levels, accessibility of the RBS and requirement for a minimum spacing of at least 7 nucleotides between the Shine-Dalgarno sequence and ATG for optimal gene expression.