A recombinant protein is a protein encoded by a gene—recombinant DNA—that has been cloned in a system that supports expression of the gene and translation of messenger RNA. Modification of the gene by recombinant DNA technology can lead to the expression of a mutant protein. Promega provides products for both the expression of recombinant proteins in cell-based E. coli systems and a variety of cell-free systems, such as rabbit reticulocyte lysate (RRL) or wheat germ extract (WGE).