Lefkowitz made a remarkable contribution in the mid-1980s when he and his colleagues cloned the gene first for the β-adrenergic receptor, and then rapidly thereafter, for a total of 8 adrenergic receptors (receptors for adrenaline and noradrenaline). This led to the seminal discovery that all GPCRs (which include the β-adrenergic receptor) have a very similar molecular structure. The structure is defined by an amino acid sequence which weaves its way back and forth across the plasma membrane seven times. Today we know that about 1,000 receptors in the human body belong to this same family. The importance of this is that all of these receptors use the same basic mechanisms so that pharmaceutical researchers now understand how to effectively target the largest receptor family in the human body. Today, as many as 30 to 50 percent of all prescription drugs are designed to "fit" like keys into the similarly structured locks of Lefkowitz' receptors—everything from anti-histamines to ulcer drugs to beta blockers that help relieve hypertension, angina and coronary disease. Lefkowitz is among the most highly cited researchers in the fields of biology, biochemistry, pharmacology, toxicology, and clinical medicine according to Thomson-ISI.