Figure 6.

Signal sequence of CpxP limits the production of MalE. (A) Schematic representation of genetic constructs using the CpxP signal sequence (pTCE), the mutated CpxP signal sequence (pTC*E), and the MalE signal sequence (pTME) fused to the mature coding sequence of MalE. (B) MacConkey agar plate showing the maltose phenotype of PM9 strain carrying pTrc99 (1), pTCE (2), pTC*E (3), and pTME (4). Overnight cultures were spotted after serial dilutions as indicated, and the plate was incubated for 24 h at 37°C. (C) PM9 strain harboring pTrc99 (1), pTCE (2), pTC*E (3), and pTME (4) was grown at 37°C with IPTG induction, then fractionated by spheroplast preparation. Periplasmic fractions normalized to the same amount of cells were separated by SDS-PAGE and stained by Coomassie Blue. The position of MalE is indicated by an arrow and the relative amount of this protein is indicated under the corresponding lane.