Background / Heterologoues expression in Escherichia coli

To characterize our metalbinding protein (T4MBP), it was necessary to produce big quantities of it. For us the method of choice was to use the bacteria Escherichia coli (E. coli). Poorly E. coli is bad in forming disulfide bonds. Because or T4MBP consists of several disulfide bonds we decided to use the Origami 2 strain, which is optimized to form disulfide bonds.

The Use of the pASK-Vector

We decided to use Tags to easily purify our protein. Therefore we used the pASK vector, because it delivers a His- and a Strep-Tag sequence. Moreover we modified the pASK plasmid with enterokinase sites (N- and C-terminus). Via enzymatically digest we are able to to get rid of the disturbing Tag regions.

Beside the His- and Strep-Tag, pASK contains an anhydrotetracyclin-promotor for the induction of the protein expression. In contrast to the lac-Promotor (inducible via e.g. lactose) the Tet-Promotor does not need a high concentration of anhydrotetracyclin to be induced. Furthermore the Tet-promotor is highly regulated and shows only a low background activity.