Analysis of a cloned sequence of Legionella pneumophila encoding a 38 kD metalloprotease possessing haemolytic and cytotoxic activities

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Abstract
The DNA encoding the zinc metalloprotease of Legionella pneumophila Philadelphia 1 has been isolated and expressed in Escherichia coli. This protein, which is 38000 Daltons in size, possesses immunological and biochemical properties identical to those previously described for the purified L. pneumophila protease. Periplasmic extracts of E. coli clones expressing the recombinant protease are also capable of causing the haemolysis of canine erythrocytes and the cytotoxic destruction of CHO cells. Using trans-poson mutagenesis, it was determined that a maximum of 1.2 kb of DNA encoded all three biological activities. Inactrvation of proteolytic activity by trans-poson insertion occurred concomitantly with losses of the haemolytic and cytotoxic phenotypes. A putative regulatory sequence approximately 200-500bp upstream of the gene's coding region was identified. A 4.0 kb fragment encoding these activities hybridized to the chromosomal DNA of the parent strain of L. pneumophila Philadelphia 1 as well as clinical isolates of L. pneumophila.