Insulin is a very important hormone. It helps move sugars and starches from the bloodstream into the cells, where they can be used for energy. People who have a disease called diabetes either do not make enough insulin or do not use it properly. They need to take insulin every day to keep their blood sugar levels under control. In the past, people with diabetes were often given insulin that was taken from animals. But sometimes their immune systems would recognize this insulin as foreign, leading to an immune reaction. In the late 1970s, scientists began using E. coli to produce insulin. The bacteria can produce recombinant insulin in large amounts. Because recombinant insulin is identical to human insulin, it does not cause an immune reaction in people who take it.
In the first step of this technology, scientists find and separate out the gene that codes for the protein they want from a human, animal, etc. E. coli carry some of their genetic information in circular pieces of DNA called plasmids. Scientists use special proteins called restriction enzymes to break apart the circular plasmid. Restriction enzymes act like scissors, cutting the plasmid at a specific sequence of bases. Then scientists insert the DNA that codes for the protein they want into the plasmid. It is glued into place using another type of enzyme (protein that speeds the rate of chemical reactions).
The plasmid is then inserted into the E. coli. The new gene causes the E. coli to produce the protein product of the gene. E. coli cells divide very quickly, making many copies of themselves. Each copy contains the new gene. E. coli works well for producing proteins because it is fast and it produces large quantities of proteins.
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