Expression of foreign antigens on the surface of Escherichia coli by fusion to the outer membrane protein TraT

The traT gene is one of the F factor transfer genes and encodes an outer me mbrane protein which is involved in interactions between an Escherichia col i and its surroundings. This protein was altered so as to permit the expres sion of foreign proteins on the outer membrane of E. coli in this study. A 729-bp DNA fragment, including the leader and entire structural gene sequen ce of traT, was amplified and obtained by PCR. This sequence was then subcl oned downstream of the tac promoter of pDR540, resulting in a TraT expressi on vector, pT2. Here, we report that the expression of TraT protein, fused either with a partial pre-S antigen of hepatitis B virus (60 and 98 amino a cids, respectively) or with the snake venom rhodostomin (72 amino acids), w as successfully achieved on the outer membrane of E. coli, using the pT2 pl asmid. This result was demonstrated using dot blot and immunofluorescence a na lysis. This finding supports the notion that the pT2 plasmid can be used as an E. coli display system. This system can detect a foreign peptide of about 100 amino acid residues in length on the bacterial surface.