A protein called the alpha-7 receptor could be key in developing drugs for medical conditions and diseases including obesity, schizophrenia, and Alzheimer"s disease. The protein is found on brain cells and is known to cause nicotine addiction. The protein interacts with 55 other proteins including a separate class of receptor that is a target for about 40 percent of all therapeutic drugs. According to researchers from Brown University the protein is like a doughnut on the surface of the cell. The hole opens when it comes into contact with neurotransmitter acetylcholine but is usually closed.