Protein-lipopolysaccharide interactions. 1. The reaction of lysozyme with Pseudomonas aeruginosa LPS

Lysozyme (EC 3.2.1.17) complexes with extracted Pseudomonas aeruginosa LPS in two distinct stages. The initial stage does not produce turbidity detectable by nephelometry (measured as nephelos units (N) per time) but does permit low-speed sedimentation of the lysozyme-lipopolysaccharide (LPS) complex. This association is 100% disrupted by the action of 0.1 M Mg2+. Monovalent cations at equal ionic strength to the Mg2+ concentration used for these studies failed to alter significantly the lysozyme-LPS complex, indicating that the role of Mg2+ was not strictly an ionic one. The study of lysozyme-LPS complexes may provide a model system for investigating in vivo protein-LPS interactions.