| Protein Microarrays |
Another strategy for the large-scale study of proteins is similar to the DNA microarrays, which measure gene expression in different cells types. (See the Genomics unit.) Based on the rapid, large-scale technology (often called high-throughput technology) that was developed for DNA microarrays, scientists have developed similar microarrays for proteins. In a protein microarray, very small amounts of different purified proteins are placed on a glass slide in a pattern of columns and rows. These proteins must be pure, fairly concentrated, and folded in their active state. Various types of probe molecules may be added to the array and assayed for ability to bind or react with the protein. Typically the probe molecules are labeled with a fluorescent dye, so that when the probe binds to the protein it results in a fluorescent signal that can be read by a laser scanner.
This technology can complement other techniques, such as mass spectrometry and yeast two-hybrid assays, to identify thousands of protein-protein interactions. Protein arrays can be screened for their ability to bind other proteins in a complex, receptors, antibodies; lipids; enzymes; peptides; hormones; specific DNA sequences; or small molecules, such as potential new drugs. One of the most promising applications for protein microarrays is the rapid detection or diagnosis of disease by identifying a set of proteins associated with the disease.
One example of the use of this technique is the development of a microarray that may help in the treatment of cancer. This microarray contains many different mutant forms of a protein called p53. P53 is an anti-cancer protein, called a "tumor-suppressor protein," and about half of all cancers have mutations in p53 (See the Cell Biology and Cancer unit.). Researchers can screen the immobilized mutant p53 proteins in the microarray for biological activity, as well as for new drugs that can restore its normal tumor-suppressing function.