A rapid method for purification of homogeneous Legionella pneumophila cytotoxic protease using fast protein liquid chromatography.

A purification method was developed to isolate Legionella pneumophila cytotoxic protease in a form suitable for biological assays. Culture supernatant of a clinical isolate of L. pneumophila, Knoxville 1 strain, was used as the starting material. The protease was purified by FPLC on a Mono Q column followed by ultrafiltration. The isolated proteolytic enzyme has a specific activity of 90 azocasein units/mg protein and is a 42 kDa monomeric protein as determined by SDS-PAGE and gel filtration chromatography. It is heat-labile and toxic to a variety of cells e.g. McCoy, SIRC, HeLa, and rhabdomyosarcoma cells, baby hamster and green monkey kidney cells, and human embryonic lung fibroblasts.