A question that often comes up from clients is what is the best signal peptide to use for baculovirus-expressed secreted recombinant proteins? While we have discussed the best flashBAC™ variant to use for the production of secreted proteins in a previous blog, we have never considered the role of the signal peptide.
In fact, while writing this blog, we realised that there was much that we didn’t know, so will publish a second more detailed blog next month when we have had the time to review some of the literature surrounding this topic.
Signal peptides are required for the entry of proteins into the cellular endoplasmic reticulum and their subsequent secretion from cells. This is a rather simplified view of their role as proteins with signal peptides may not always be secreted but retained in other compartments of the cell. However, for the purposes of this brief blog we will consider their function in baculovirus-expressed secreted recombinant proteins.
A common misconception is that you can add a signal peptide to any recombinant protein and get secretion of the target from the cell. This may work for small, simple proteins, but is unlikely to be successful for large, complex proteins. These proteins may have other signals within their sequence that tell it to go somewhere else in the cell. Therefore, beware the temptation to add a signal peptide coding sequence to your synthetic gene in the expectation that the resultant protein will then be secreted.
If your target gene sequence already has a signal peptide coding region, we suggest you use this one as a default. There are several insect-specific secretion signal peptides that can be used, but there is no guarantee that these will outperform what evolution has selected over many millions of years. You might add a heterologous signal peptide coding region and find that your target protein isn’t secreted at all owing to possible changes in protein conformation.
So watch out for our blog continuation next month when we will consider some of the published work on baculovirus-expressed secreted recombinant proteins.