Expression of Chemokines in the Periplasmic Space of E. coli

Here we describe the expression of chemokines in the periplasmic space of Escherichia coli (1 –3 ), which leads to correctly folded proteins with no N-terminal modifications, in the case of RANTES, and with a yield of several hundred micrograms from a 1-L culture. Other expression systems that are generally used for the production of chemokines have several disadvantages. Bacterial expression in the cytoplasm of E. coli (4 ,5 ) gives large yields, but sometimes leads to an additional methionine at the N-terminus (6 ). Furthermore it requires an extensive refolding protocol, because disulfide bonds generally do not form in the cytoplasm, resulting in an incorrect protein conformation. Refolding is also necessary for chemically synthesized chemokines (7 ). Eucaryotic expression gives rise to correctly folded proteins, but has low yields, and secreted chemokines are often subject to proteolysis. In the case of RANTES expressed in CHO cells, a high proportion of the protein lacks the first two or three N-terminal amino acids.