Expression of Recombinant Proteins From lac Promoters

The Gram-negative bacterium Escherichia coli enjoys widespread use in modern biology as both a model organism and a microbiological tool. One of the keys to its popularity lies in the functionality of the lac operon. This regulated E. coli operon has been manipulated and utilized in diverse and creative ways since it was first studied by Jacob and Monod in 1961 (1 ). Excellent in-depth reviews of the lac operon and its uses in classical genetics are provided in refs. 2 and 3 . Its enduring use can be attributed to the development of a wide range of engineered mutants and plasmid constructs designed to take advantage of specific features of the operon, particularly its inducibility by β-galactosides. This chapter will focus on the use of the lac operon in E. coli protein expression, although it has also been utilized for protein expression in mammalian systems (4 ). The application of lacZ as a reporter gene is discussed in Chapter 30 .