Many important pharmaceutical protein, such as antibodies and insulin, are derived from mammalian organisms. These mammalian cells have organelles that isolate a special environment for proteins to fold correctly and form disulfide bonds, such as the endoplasmic reticulum. Yet, mammalian cells take a long, difficult time to grow and are not ideal for industrial production of pharmaceutical proteins. Fast growing organism such as E.coli presented us with the grand advantage of producing and purifying large amounts of protein in a short amount of time but prokaryotes don’t have the organelles capable of properly folding pharmaceutical proteins.

Disulfide bonds occur naturally in E.coli in the periplasm. The periplasm has an oxidizing environment, similarly to the endoplasmic reticulum, that allows disulfide bond formation. If we drive a mammalian protein through the periplasm of an E.coli cell it will able to fold properly by disulfide bond formation.

Antibodies have become paramount in biotechnology and medicine. Table 1 ranks the companies with the highest sales in March 2014; as we can see, 3 companies out of the top 10 sell antibody fragments. This reveals the impact of purification system improvement.

In our project, we've purified antibody fragments by tagging a secretion protein, OsmY, to an antibody scFv (single chain fragment variable) and over-expressing the construct in E. coli. To demonstrate the importance of our study we've chosen an antibody specific to DADH, a Salmonella protein. Salmonella is responsible for 23,000 hospitalizations in the US each year, highlighting the need for large quantities of inexpensive sensors. To further demonstrate the value of our part we've compared our secretion system with industrially used secretion system that use the secretion tag pelB.

Table 1