A happy new year to you all!

We are presently trying to express a viral glycoprotein in CHO and HEK cells, but it gives quite a poor yield of secreted protein. We do see quite a bit of protein in the cell lysate, indicating that there is a folding/secretion problem. We have used IgG Fc as a fusion tag and it helps to get a better secretion, but for different reasons we don't want to use Ig Fc as a fusion partner in the protein for later use of the protein.

I know there are some other fusion partners that can be used in mammalian cells, but I would like to know if anyone of you has good (or bad) experience with any other such tag. Has anyone tried the HaloTag in mammalian cells? Any other tags? I would be grateful for suggestions and comments!

Malin Bäckström

Dear Malin,

we have so far used C-terminal His8Tag (pTT21) and C-terminal OneStrep Tag succesfully for secreted proteins in HEK293E / pTT vectors.

We have also validated several other C-terminal tags in pTT, but only for eGFP (S-Tag, CBP Tag, HPC Tag, His10) In our hands OneStrep and His10 worked best for eGFP.  No data so far for secreted proteins

N-terminally tagged : we have ß-tested the promotor variations of Halo Tag in the Promega vectors for an intracellular test protein. However, we could not release the protein from the beads, and Promega had replied that the TEV site still needs to be optimized. As we had already invested quite some time for Halo tag in E.coli expression (strong mutation tendendy in the tag) we discontinued HaloTag testing in any host.

Sorry, there is not more that we had tested.

Best

Sabine