Human Insulin

Insulin is a peptide hormone produced by the beta-cells of the islets of Langerhans in the pancreas; it was discovered by Sir Edward Sharpey-Schafer in 1916, while he was studying the islets of Langerhans. Insulin is essential for controlling blood sugar levels, and diabetes mellitus is the disease in which some people cannot make enough insulin themselves.

Step 1. Hakura and co-workers (1977) chemically synthesised the DNA sequences coding for insulin's two chains, A and B.

Step 2. These two sequences were inserted separately into two different pBR322 plasmid vectors, with each chain's gene placed next to a beta-galactosidase gene in its own plasmid.

Step 3. The two recombinant plasmids were then separately transformed into E. coli host cells.

Step 4. Each transformed host produced a fusion product -- penicillinase joined to pre-pro-insulin. …