Partial characterization of peptidoglycan-associated proteins of Legionella pneumophila

The proteins associated with the peptidoglycan (PG) of Legionella pneumophila are resistant to proteolysis by trypsin, protease VI and proteinase K. These protease-resistant proteins are associated with the PG noncovalently and covalently. Analysis of cell walls and PG-protein complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions revealed one major protein (38.5K) and several minor Coomassie and silver staining components. The 38.5K protein seemed to be a major component which was co-purified with the PG. The cleavage of the PG-protein complex by 1 N NaOH treatment yielded PG free of proteins which was subjected to alkali hydrolysis. This association of PG and protease-resistant covalently-bound proteins may be an important structural and functional determinant of resistance to both environmental conditions and intracellular digestion of L. pneumophila by eukaryotic cells.