Description of a putative type I secretion system in Legionella pneumophila.

Abstract Here we describe the first putative type I secretion system of L. pneumophila . The lssXYZABD locus was found to be present in all L. pneumophila strains tested so far. The LssB and LssD proteins are homologues to the proteins of type I secretion systems of Vibrio cholerae and Salmonella typhi . The expression of the gene locus was analysed by RT-PCR. Three polycistronic transcripts could be identified. Comparison of the lss locus of L. pneumophila Philadelphia I with that of L. pneumophila Corby revealed protein identities of 97 to 99%, except for LssE proteins that were only 78.6% identical. Computer analysis of the amino acid sequence of LssE identified it as a putative signalling protein.