Figure 4.

The SecA N-terminus is Essential for Function To test the functionality of SecA constructs, BL21.19(DE3) cells, in which expression of SecA is temperature-sensitive such that the cells do not grow at 42 °C⁴³, were transformed with plasmids that express SecA, SecA-N95, or the same constructs but with 14 residues deleted at the N-terminus, SecA∆N and SecA-N95∆N. The cells were grown in liquid culture for 12 hours and diluted to a common OD₆₀₀ of 1, followed by 5 subsequent 10-fold dilutions; 5 µL of the resulting liquid cultures were spotted onto LB-agar and grown at either 28 °C or 42 °C for 30 hours in the absence or presence of IPTG (500 µM).