Protein A as a fusion partner for the expression of heterologous proteins in Lactobacillus.

An expression system based on the Staphylococcus aureus protein A gene (spa) was developed to allow the production and export of proteins in Lactobacillus. Plasmid shuttle vectors were constructed that carried the eZZ gene, a synthetic gene based on the Protein A gene (spa) but lacking the carboxy-terminal membrane-anchoring region. A gene fusion was created between the eZZ gene and the VD4 region of a chlamydial major outer-membrane protein gene. Expression studies demonstrated the recognition of the spa regulatory signals by several Lactobacillus, with the recombinant protein being expressed (from 0.1 microgram of EZZVD4 fusion protein per ml in L. plantarum up to 10 micrograms of EZZ protein per ml in L. fermentum) and exported (levels up to 20% in L. fermentum) in several Lactobacillus strains.