Influence of single base change in Shine-Dalgarno sequence on the stability of B. subtilis plasmid PSM604

B. Subtilis expression plasmids generally require a stringent Shine-Dalgarno Sequence (SDS). Site-directed-mutagenesis was explored to change the Shine-Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (wild type) in recombinant plasmid PSM604. The single base substitution made the plasmid with wild SDS unstable in structure and segregation. The interaction of SDS with subtilisin leader sequence of PSM604 might be responsible for the instability of plasmid.