Method and vector for the purification of foreign proteins

Abstract

The present invention provides an method for isolating and purifying recombinantly produced proteins. This invention involves the use of an expression vector which includes a nuclear targeting signal sequence which effectively directs newly synthesized proteins to the nucleus; a cleavage recognition sequence which cleaves specifically at a pre-determined cleavage site after addition of a viral enzyme; and a cDNA sequence which codes for a desired protein. Specifically the production and isolation of a desired protein is accomplished through the use of lepidopteran cells transfected or infected with recombinant baculovirus expression vector comprising a polyhedrin gene derived nuclear targeting signal sequence and a cleavage recognition sequence derived from a potyvirus polyprotein. The newly synthesized proteins are directed into the nucleus whereupon nuclear protein is extracted from the nucleus. Thereafter the desired protein is bound to an affinity matrix embedded with antibodies directed against the nuclear targeting sequence. Afterwards the desired protein is cleaved from the affinity matrix with the addition of a viral enzyme.