Production of heterologous proteins in Bacillus subtilis: the effect of the joint between signal sequence and mature protein on yield.

We have previously made a set of DNA constructs by fusing the mature part of Bacillus licheniformis alpha-amylase with the signal sequence of B. amyloliquefaciens alpha-amylase at various distances from the signal sequence cleavage site. We observed that the level of alpha-amylase production in B. subtilis depended strongly on the distance of the junction from the signal sequence cleavage site, with quite a sharp optimum distance. To test whether the effect is limited to the pair of alpha-amylase signal sequence and mature protein, we analysed the protein production in a set of constructs in which an Escherichia coli beta-lactamase was similarly joined at different distances from the alpha-amylase signal sequence. Also in this case the distance seemed to be an important factor in affecting the level of production in B. subtilis. The observed effect might depend on the modulation of pre-protein folding, which in turn could affect the secretion level.