Pan-African flag - History. 1  The flag was created in 1920 by members of UNIA in response to the enormously popular 1900 coon song Every Race Has a Flag but the Coon. [4] which has been cited as one of the three songs that firmly established the term coon in the American vocabulary.
A ligand is any molecule that binds to a specific site on a protein or other molecule. In this case, the estrogen hormone 17-beta-estradiol is the ligand, and the estrogen receptor is the protein. Binding turns on, or activates, a hormone receptor.
Interestingly, growth hormone must bind to two receptor molecules simultaneously to mediate its function. The hormone binds on the outside of the cell, bringing two receptors together. PDB entry 3hhr , shown here, includes the extracellular portion of two receptors bound to growth hormone.