Lefkowitz started to trace cell receptors in 1968. Using radioactivity, he managed to unveil several receptors, including one for adrenalin, the β-adrenergic receptor. His team then extracted the receptor from the cell membrane and forged an initial understanding of how it works.
In the 1980s, Kobilka, then a postdoc at Duke, isolated the gene that codes for the β-adrenergic receptor, and found that the receptor was similar to one in the eye that captures light. They also realized that the β-adrenergic receptor was one of many in a whole family of receptors that function in the same way.
This family is now known as G-protein-coupled receptors, and the studies by Lefkowitz and Kobilka have been crucial to understanding how they function. The insights have been critical to drug discovery, among other areas of research, as around half of all drugs currently available work by targeting these receptors.