1 Key and Criteria to the Selection of an Expression Platform
Gerd Gellissen, Alexander W.M. Strasser, and Manfred Suckow
The production of recombinant proteins has to follow an economic and qualitative rationale, which is dictated by the characteristics and the anticipated application of the compound produced. For the production of technical enzymes or food additives, gene technologymust provide an approach which has to compete with the mass production of such compounds from traditional sources. As a consequence, production procedures have to be developed that employ highly efficient platforms and that lean on the use of inexpensive media components in fermentation processes. For the production of pharmaceuticals and other compounds that are considered for administration tohumans, the rationale is dominated by safety aspects and a focus on the generation of authentic products. The demand for suitable expression systems is increasing as the emerging systematic genomics result in an increasing number of gene targets for the various industrial branches (for pharmaceuticals, see Chapter 16). So far, the production of approved pharmaceuticals is restricted to Escherichiacoli, several yeasts, and mammalian cells. In the present book, a variety of expression platforms is described ranging from Gram-negative and Gram-positive prokaryotes, over several yeasts and filamentous fungi to mammalian and plants cells, thus including greatly divergent cell types and organisms. Some of the systems presented are distinguished by an impressive track record as producers ofvaluable proteins that have already reached the market, while others are newly defined systems that have yet to establish themselves but demonstrate a great potential for industrial applications. All of them have special favorable characteristics, but also limitations and drawbacks – as is the case with all known systems applied to the production of recombinant proteins. As there is clearly no singlesystem that is optimal for all possible proteins, predictions for a successful development can only be made to a certain extent, and as a consequence misjudgments leading to costly time- and resource-consuming failures cannot be excluded. It is therefore advisable to assess several selected organisms or cells in parallel for their capability to produce a particular protein in desired amounts andquality (see also Chapter 13). The competitive environment of the considered platforms is depicted in Table 1.1. A cursory correlation exists between the complexity of a particular protein and the complexity and capabilities of an expression platform. Single-subunit proteins can easily be produced in bacterial hosts, whereas proteins that require an authentic complex mammalian glycosylation or thepresence of several disulfide bonds necesProduction of Recombinant Proteins. Novel Microbial and Eucaryotic Expression Systems. Edited by Gerd Gellissen Copyright # 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-31036-3
1 Key and Criteria to the Selection of an Expression Platform Table 1.1 Some key parameters for the choice of a particular expression system. The column“Expression system” provides the list of the systems described in the various chapters of this book. The column “Classification” provides a rough classification of these organisms. The coloring of the fields indicates the complexity of the respective organism, increasing in the order light gray, medium gray, dark gray. In the following columns, positive and negative aspects are distinguished by the coloringof the fields. Light gray indicates negative, and dark gray positive features. Fields in medium gray indicate an intermediate grading. The column “Development of system” distinguishes between “early stages” and “completely developed”. The latter indicates that the full spectrum of methods and elements for genetic manipulations, target gene expression, and handling is available. “Early stages”...