Expression of Envelope Gene gp85 of Avian Leukodls Virus in E．coli

A part of the cloned fragment was excised from the recombinant with Bgl II and Sal I and subcloned into the expression vector pET-21d (+) to yield another recombinant named pET-21d-RAV-1 env (Bgl II/Sal I). The recombinant was sequenced and the result showed that the inserted fragment was identical to the counterpart in RAV-1 env gene both in nucleotide sequence and open reading frame. The E.coli BL2 (DE3) transformed with recombinant plasmid were induced with 1 mmol/L IPTG and the expression product found to be 20 kD in size on SDS-PAGE. The size of the expression product was the same as that theoretically calculated. In addition, the effects of start time and duration for IPTG induction on expression efficiency were analyzed and the result indicated that the start time for IPTG induction was more important to high expression efficiency than its duration.