[Study of a lipid A-protein complex from Yersinia pseudotuberculosis endotoxin]

Mild acid hydrolysis of endotoxin of Yersinia pseudotuberculosis afforded a lipid A--protein complex composed of amino acids and all characteristic components of lipid A: glucosamine, dodecanoic, 3-hydroxytetradecanoic acids and phosphorus in a molar ratio of 2 : 1,5 : 2,8 : 1,7, respectively. The protein component of the complex was shown by gel electrophoresis in the presence of sodium dodecylsulphate to consist of two polypeptides with apparent molecular weights of 12000 and 8000. The lipid A--protein complex cross-reacted with antiserum to endotoxin and lipid A antiserum. The components of the complex, namely lipid A and a protein, are associated tightly but noncovalently and can be separated by ultracentrifugation in the sucrose density gradient after treating the complex with sodium dodecylsulphate. The resultant lipid A and the protein manifest a serological activity.