Proteins in a DNA world: expression systems for their study.

Every day, new proteins are discovered and the need to understand its function arises. Human proteins have a special interest, because to know its role in the cell may lead to the design of a cure for a disease. In order to obtain such information, we need enough protein with a high degree of purity, and in the case of the human proteins, it is almost impossible to achieve this by working on human tissues. For that reason, the use of expression systems is needed. Bacteria, yeast, animals and plants have been genetically modified to produce proteins from different species. Even "cell-free" systems have been developed for that purpose. Here, we briefly review the options with their advantages and drawback, and the purification systems and analysis that can be done to gain understanding on the function and structure of the protein of interest.