Versatility of a vector for expressing foreign polypeptides at the surface of gram-negative bacteria.

A wide variety of peptides in terms of length and sequence can be expressed at the surface of the bacterium Escherichia coli by genetic insertion into a 'permissive' site of the outer membrane protein LamB, used as a carrier. The resulting hybrid proteins essentially keep their biological activities with inserts of up to about 60 amino acid residues, and of a large range of predicted structures or hydrophobicities. This reflects a remarkable flexibility in the organization of the protein, but also in the export machinery. The method used to select such a permissive site is quite general and its potential to generate applications, including a versatile type of live bacterial vaccine, are discussed.