Understanding allosteric and cooperative interactions in enzymes.

The paper that introduced biochemists to the idea of allosteric feedback inhibition [Monod J, Changeux J-P & Jacob F (1963) J Mol Biol 6, 306-329] is now 50 years old, and the two papers on models for enzyme cooperativity that followed it [Monod J, Wyman J & Changeux J-P (1965) J Mol Biol 12, 88-118; Koshland DE, Némethy G & Filmer D (1966) Biochemistry 5, 365-385] are almost as old. All of these papers continue to be heavily cited today - more in the 21st century than they were in the last two decades of the 20th. This is because they continue to be central for understanding enzyme regulation, and increasingly important in the age of systems biology.