Open AccessStudies on the Protein Moiety of Endotoxin from Gram‐Negative Bacteria
Author(s) -
Wober Wolfgang,
AlaupoviĆ Petar
Publication year - 1971
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1971.tb01324.x
Subject(s) - pronase , lipid a , conjugated system , chemistry , biochemistry , serratia marcescens , hydrolysis , trypsin , bacteria , organic chemistry , enzyme , biology , escherichia coli , gene , genetics , polymer
Conjugated protein isolated from the endotoxin complex of Serratia marcescens 08 by 1% acetic acid hydrolysis was characterized by analytical ultracentrifugation, electrophoretic and immunological properties and chemical analysis. The chemical composition of conjugated protein and other degraded fragments of endotoxin showed that all characteristic constituents of lipid A were present exclusively in conjugated protein. Successive treatment of conjugated protein with trypsin and pronase resulted in the isolation of corresponding tryptic and pronase cores which were characterized by an increased content of lipid A constituents. Lipid A was separated as an entity from the conjugated protein only after hydrolysis with 0.1 N hydrochloric acid. This result confirms our previous proposal that lipid A is covalently linked to the protein moiety in whole endotoxin of S. marcescens 08. “Conjugated” protein isolated by acetic acid hydrolysis and “simple” protein prepared by hot aqueous phenol treatment of whole endotoxin differ from one another not by the presence or absence of lipid A but rather by the presence of the entire lipid A moiety in the conjugated protein and only a fragment of lipid A in the simple protein. Conjugated protein and its tryptic and pronase cores were immunogenic and possessed a common antigenic determinant with simple protein and its corresponding cores. Toxicity studies revealed that both conjugated and simple proteins retained to different degrees the toxic properties of whole endotoxin. Sodium dodecyl sulfate had an enhancing rather than diminishing effect on the toxicity of endotoxin and its various fragments. The importance of lipid A as the toxic factor of endotoxins was established not only indirectly by determining the toxicity of each fragment containing lipid A, but also directly by demonstrating that lipid A dispersed in a Tris‐dodecyl sulfate buffer displayed toxic properties similar to those of the lipopolysaccharide preparation.