Characterisation of protein co-extracted together with LPS in Escherichia coli, Salmonella minnesota and Yersinia enterocolitica.

The porin proteins of Escherichia coli, Yersinia enterocolitica, and Salmonella minnesota were found to co-extract by the phenol-chloroform-petroleum ether method together with the R lipopolysaccharide of these strains. Lipopolysaccharide free protein recovered from the phenolic residue of the phenol-chloroform-petroleum ether extract migrated as a Mr 36-37,000 protein. We could demonstrate that the protein was extracted from bacteria as a high molecular weight protein-lipopolysaccharide complex. Once exposed to phenolic conditions, the protein was no longer soluble in the phenol-chloroform-petroleum ether extraction mixture, indicating a highly specific lipopolysaccharide-protein association.