A λgt11 library constructed with Leptospira borgpetersenii DNA was screened with monoclonal antibodies (mAb) recognizing a periplasmic flagella-associated protein. A plaque expressing a fusion protein (λF15) which reacted with the mAb was isolated and the nucleotide sequence analyzed. The deduced amino-acid (aa) sequence indicates that thepfaP gene belongs to a group of bacterial genes whose products share aa sequence and possibly functional homologies with sppA, an Escherichia coli signal peptidase-encoding gene.