Heterologous Expression of Genes in Bacterial, Fungal, Animal, and Plant Cells

Analysis of gene function is of central importance for the understanding of physiological processes. Expression of genes in heterologous organisms has allowed the isolation of many important genes (e.g. for nutrient uptake and transport) and has contributed a lot to the functional analysis of the gene products. For animal research, expression in Xenopus oocytes and cell cultures are predominant techniques, whereas in the plant domain, yeast has become the prevalent expression system. This review provides a survey of this quickly developing field and intends to assist researchers in determining appropriate experimental approaches for specific biological questions. Because heterologous expression technology is of special value for the analysis of proteins that are difficult to handle biochemically, the examples given concentrate on membrane proteins, i.e. transporter proteins. Also included is a detailed discussion of the functional expression methodology and its use in identifying and characterizing genes and proteins.