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Production of Recombinant Proteins

The most widely used and most important expression systems are those using E. coli as the host cell. An overview of the production of proteins in E. coli is provided in UNIT 5.1. General strategies for gene expression described include direct intracellular expression, secretion of the protein into the periplasmic space, and the expression of fusion proteins. Some of these strategies (e.g., secretion procedures) are used to overcome the common problem of inclusion body formation (see UNIT 6.1 for additional discussion); others (e.g., fusions involving affinity tags) are used simply to assist in protein purification. Many of the expression vectors discussed are commercially available and suppliers are indicated throughout the text.