Studies on the Protein Moiety of Endotoxin from Gram-Negative Bacteria: Characterization of the Enzymatically Degraded Protein Moiety Isolated by Phenol Treatment of Endotoxin from S. marcescene 08
OKLAHOMA UNIV MEDICAL CENTER OKLAHOMA CITY
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The simple protein of endotoxin from Serratia marcescens 08 was treated successively with trypsin and pronase. The resulting trypsin and pronase cores contained increasing amounts of lipid A constituents firmly bound to the residual protein moiety. Since lipid A was separated as an entity from the protein moiety only after acid hydrolysis of the pronase core, it is proposed that in intact endotoxin lipid A is covalently linked to the protein moiety. The absence of any detectable glucosamine and fatty acids in the mixture of peptides and amino acids released by trypsin and pronase, indicated a single point attachment between the lipid A and protein moieties. Both trypsin and pronase cores were immunogenic and revealed the presence of a common antigenic determinant with the parent simple protein. The second set of antigenic determinants different from the specific O-antigens is located in the protein moiety close to lipid A.