 He is also a Professor of Biochemistry and a Professor of Chemistry.He has been an Investigator of the Howard Hughes Medical Institute since 1976 and was an Established Investigator of the American Heart Association from 1973-1976.Lefkowitz studies receptor biology and signal transduction and is most well known for his detailed characterizations of the sequence, structure and function of the β-adrenergic and related receptors and for the discovery and characterization of the two families of proteins which regulate them, the G protein-coupled receptor (GPCR) kinases and β-arrestins.