Vectors for Expressing Open Reading Frame DNA in Escherichia Coli Using lacZ Gene Fusions

Abstract

One of the important advances of genetic engineering is the ability to express cloned DNA segments in a surrogate host such as Escherichia coli. To accomplish this heterologous gene expression, bacterial initiation signals for transcription and translation must be spliced to the foreign coding sequence to create gene fusions. To produce a complete protein, the fusion joint must be at the start of the foreign gene. This requires precise splicing and can involve considerable effort. A simpler approach, requiring less precision, is to create the fusion joint somewhere within the target gene. In this case a hybrid protein is made containing a bacterial peptide at its N terminus joined to the C-terminal portion of the foreign polypeptide. Although such hybrid proteins do not in general retain the activity of the foreign protein, they can nevertheless be valuable when the normal protein is not required. Hybrid proteins are a source of the foreign antigen that can be used to produce antibodies for research, for applications such as the identification of gene products, or as diagnostics in medicine. In addition, although hybrid proteins are not usually active biochemically, there are numerous examples of hybrids that exhibit some activities of the complete protein. Thus, hybrid proteins can also be useful biochemical reagents.