The pAS vector system and its application to heterologous gene expression in Escherichia coli

There are numerous proteins of biological interest which cannot be obtained from natural sources in quantities sufficient for detailed biochemical and physical analysis. The limited bioavailability of these molecules has made it impossible to consider their potential utilization as either pharmacological agents and/or targets. One solution to this problem has been the development of recombinant vector systems which are designed to achieve efficient expression of cloned genes in a variety of biological systems. This paper will describe the development and application of a particular set of vectors which have been designed to achieve efficient expression of essentially any gene coding sequence in Escherichia coli. The system utilizes efficient phage-derived transcriptional and translational regulatory signals and provides a strong regulatable promoter, an antitermination mechanism to ensure efficient transcription across any gene insert, high stability and, when appropriate, efficient translation initiation information. In addition, a wide variety of host strains have been developed in order to help control, stabilize and maximize expression of various cloned genes. The system has now been used to express efficiently more than 75 different prokaryotic and eukaryotic gene products. The application of this system to the expression and characterization of several oncogene products will be described.