Expression of plant proteins in baculoviral and bacterial systems

This chapter discusses the expression of plant proteins in baculoviral and bacterial systems. Escherichia coli (E. coli) are widely used for the expression of heterologous proteins. The advantages of E. coli are the ease of handling, speed, low cost, high yields, and the choice of a variety of versatile vector/strain systems. Potential disadvantages of E. coli are the lack of eukaryote-specific protein modifications and the phenomenon that heterologous proteins frequently do not fold correctly, particularly at high expression levels, and accumulate in insoluble form. Many functionally different plant proteins have been expressed in the T7 system. A number of them were soluble and similar, if not identical, to the authentic protein. However, there are only a few reports concerning the successful renaturation of aggregated, inactive plant proteins. Potential advantages of baculovirus include the strength of the polyhedrin promoter that is used to transcribe the gene of interest, the capability of the infected insect cells to accomplish most eukaryotic post-translational protein modifications, and the biological safety of the vector system, as the virus cannot replicate or express its DNA in mammalian cells. However, compared with E. coli, in the baculovirus system the work is much slower and more laborious, equipment for cell culture work is required, and media and other materials are expensive. Therefore, the baculovirus system usually is the expression system of choice if the protein of interest expressed in E. coli is not functional. © 1995, Academic Press, Inc.