title: Sensitivity of Coxiella burnetii peptidoglycan to lysozyme hydrolysis and correlation of sacculus rigidity with peptidoglycan-associated proteins.
abstract: The protease-resistant proteins associated with the peptidoglycan (PG) of the phase I small-cell variant Coxiella burnetii were either partially released from the PG by boiling the PG-protein complex (PG-PC) in sodium dodecyl sulfate containing 2-mercaptoethanol and EDTA or totally released by 1 N NaOH hydrolysis at 23 degrees C. An 18,300-dalton protein was released from the PG-PC under reducing conditions, whereas 1 N NaOH treatment extracted PG-associated proteins without apparent dissolution of the PG. Purified PG was composed of muramic acid, glucosamine, glutamic acid, alanine, and meso-diaminopimelic acid in a molar ratio of 0.9:0.9:1.0:1.4:1.0. Lysozyme hydrolysis of cell walls, PG-PC, and purified PG caused an increase in reducing groups which correlated with roughly 60 to 100% digestion of disaccharides. There was no significant decrease in turbidity during lysozyme hydrolysis of cell walls and PG-PC; however, hydrolysis of purified PG caused about 90% decrease in turbidity. Approximately 60% of the meso-diaminopimelic acid groups of PG were not susceptible to dinitrophenylation, thus, demonstrating an apparent contribution of PG-associated proteins, rather than cross-linkage between peptides, to sacculus rigidity of cell wall and PG-PC. This association of PG and protease-resistant covalently bound proteins may be important structural and functional determiners of resistance to both environmental conditions and intracellular digestion of C. burnetii by eucaryotic cells.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002473:Cell Wall / Q000648:ultrastructure*; D003381:Coxiella / Q000648:ultrastructure*; D004591:Electrophoresis, Polyacrylamide Gel; D005944:Glucosamine / Q000032:analysis; D006868:Hydrolysis; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification; D009113:Muramidase / Q000378:metabolism*; D010457:Peptidoglycan / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D008565:Membrane Proteins; D010457:Peptidoglycan; D009113:Muramidase; D005944:Glucosamine