In the late 1950s and early 1960s, the French molecular biologists
François Jacob and
Jacques Monod became the first to explain enzyme induction, in the context of the
lac operon of
Escherichia coli. In the absence of lactose, the constitutively expressed
lac repressor protein binds to the operator region of the DNA and prevents the transcription of the operon genes. When present, lactose binds to the lac repressor, causing it to separate from the DNA and thereby enabling transcription to occur. Monod and Jacob generated this theory following 15 years of work by them and others (including
Joshua Lederberg), partially as an explanation for Monod's observation of
diauxie. Previously, Monod had hypothesized that enzymes could physically adapt themselves to new substrates; a series of experiments by him, Jacob, and
Arthur Pardee eventually demonstrated this to be incorrect and led them to the modern theory, for which he and Jacob shared the 1965
Nobel Prize in Physiology or Medicine (together with
André Lwoff). •
Aryl hydrocarbon receptor ==Potency==