Export of Bordetella pertussis serotype 2 and 3 fimbrial subunits by Escherichia coli

Bordetella pertussis serotype 2 and 3 fimbrial subunits were expressed and exported in Escherichia coli using the recently described expression/secretion vector pCGV1. Two protease deficient E. coli strains (CAG629 and EC538) and two periplasmic-leaky mutants (AE84064 and A593) were transformed with the different constructs and, after thermal induction, proteins present in the various cellular compartments were analyzed by Western blot. The results obtained with the two types of fimbrial subunits were generally the same: a recombinant protein of the expected molecular mass (19.2 kDa) was present in the periplasm of the leaky mutants and of CAG629 strain (Ion protease- and heat shock protease-deficient). Only the expression of the recombinant fimbrial subunits by the tolB A593 mutant resulted in protein release into the extracellular medium. These results indicate that the use of hybrid plasmids based on pCGV1 in combination with the tolB mutant constitute an efficient system for the export of recombinant proteins.