4. Mammalian cells as a Expression System

E.COLI as a Expression System

An Over-view of protein synthesis machinery in E.coli - Protein production in prokaryotic system is a multistep process and an over-view of these steps are as follows:

1. Binding of RNA polymerase to the promoter elements to start the transcription to form m-RNA.

2. As soon m-RNA is synthesized, a translation machinery start the synthesis of protein. Protein synthesis start usually at the start codon AUG and ends at the stop codon (UAA, UGA or UAG). In bacteria transcription and translation occurs simultaneously and translation start as soon as m-RNA comes out from the RNA polymerase.

The details of these steps can be followed from any molecular cell biology text book such as, B. Alberts, A. Johnson, J. Lewis, M. Raff, K. Roberts, P. Walters, Molecular Biology of Cell, 5 th Ed, Garland Publishing, 2007.

Figure 24.1: Steps of protein synthesis in e.coli expression system.