Recombinant protein expression

Recombinant proteins are widely used in biological and biomedical research[1], and recombinant protein expression has become a commonly used tool. Nevertheless, there are still many aspects to consider before starting an expression project. For example, which expression system is chosen for obtaining the protein of interest? Should it be expressed in bacteria, in yeast, in insect cells or in mammalian cells? What is the best expression vector to be used? As to the bacterial expression system, which strain should be chosen? Is there any differences in the expression condition between the full-length protein and a protein fragment? Which affinity tag should be used to facilitate both protein expression and subsequent purification steps? How to work out an appropriate purification strategy? Since protein property can vary a lot, all conditions need to be carefully chosen to fit the project requirements.