Nucleotide sequence analysis of the Legionella micdadei mip gene, encoding a 30-kilodalton analog of the Legionella pneumophila Mip protein. Infect. Immun

After the demonstration of analogs of the Legionella pneumophila macrophage infectivity potentiator (Mip) protein in other Legionella species, the Legionella micdadei mip gene was cloned and expressed in Escherichia coli. DNA sequence analysis of the L. micdadei mip gene contained in the plasmid pBA6004 revealed a high degree of homology (71%) to the L. pneumophila mip gene, with the predicted secondary structures of the two Mip proteins following the same pattern. Southern hybridization experiments, with the plasmid pBA6004 as the probe, suggested that the mip gene of L. micdadei has extensive homology with the mip-like genes of several Legionella species. Furthermore, amino acid sequence comparisons revealed significant homology to two eukaryotic proteins with isomerase activity (FK506-binding proteins). The intracellular life-style of at least two Legionella spe-cies encountered in human infection, Legionella pneumo-phila and L. micdadei, is well established (13, 15, 16, 22, 25). When a human is the host organism, the bacteria are phagocytized by alveolar macrophages. Once inside, the bacteria prevent lysosome-phagosome fusion by a yet-un-known mechanism, thus evading one possible route o