Suppose you are given the task of genetically modifying a mouse so that its skin cells secrete a bitter tasting protein that will protect it from predation. What factors would you have to consider in order to achieve this goal? You only need to consider protein targeting, do not be concerned with how you would get the gene into the mouse or how you would control expression of the gene once it is in the mouse.
Given that correct expression of the gene is not a concern, the first consideration is whether the protein can actually be produced by the cells, i.e. whether it may have cytotoxic effects. To address this, the transgene should be tested in a cell culture system to assess any potential cytotoxicity prior to generating the animal.
<br>Secondly, the protein must undergo any necessary post-translational modifications (such as serine or threonine phosphorylation, or glycosylation) and assume the correct secondary and tertiary structure. If the gene is derived from a mammalian system this should not be a problem, as the appropriate signals will be present to ensure correct modification and chaperonin proteins will assist in folding if necessary (small proteins do not usually require this).
<br>Finally, the protein must be correctly targeted to the secretory pathway so that it is secreted by the skin cells.
<br>Protein trafficking and targeting within the cell is controlled by signal peptides and ...