A protein ligand binds to receptor sites on the surface of a protein. Ligands are involved in a wide variety of processes, from protein folding to change structure and they provide a function in immune reactions. They are a topic of close study in research facilities, as they play an important role in health care applications. Custom-designed medications can take advantage of research about a protein ligand, for example. These structures can also offer insight into the function of different proteins.
Atoms, molecules, and ions can all act as protein ligands. A classic example is an antibody. Antibodies lock on to receptor sites on the surface of proteins like those found studding the external envelope of viruses. Enzymes and a number of other structures inside the body make use of the protein ligand in their construction to enable various functions.
In scientific research, people can look at a protein to identify potential binding or docking sites. The location of sites can provide information about what kind of protein it is, and what functions it is supposed to perform in the body. This search can also be done in reverse, by identifying ligands and finding out what they can potentially bind to as they circulate through the body. Some ligands have a broad spectrum of action and can connect to a number of different proteins, while others are extremely precise.
Drug development uses protein ligand research. Pharmaceutical companies need to identify targets on cells and structures like viruses in order to effectively treat patients. By finding a protein unique to a particular organism, for example, the company can develop a protein ligand that will latch onto it, carrying medication to kill the organism or stop its reproduction. Identification of target proteins can help with the development of vaccines as well.
These structures can also be of interest for companies that develop laboratory tests. A test can take advantage of known ligands and proteins to flag structures of interest in a sample. For example, if a doctor wants to find out whether a patient has a viral infection, the lab can introduce ligands with tags that fluoresce. If viruses are present in the sample, the ligands latch on and light up to show the presence of infection.
Databases of proteins and accompanying ligands are available. Many are free to use, in the interest of advancing scientific research. Private databases maintained by drug companies can contain proprietary information used in drug development. In the process of applying for patents, the company must explain how a drug works and this can provide information about the target used, allowing other companies to take the research even further.