Proteins released from cell envelopes of Pseudomonas aeruginosa on exposure to ethylenediaminetetraacetate: comparison with dimethylformamide-extractable proteins.

Abstract

Isolated cell envelopes of Pseudomonas aeruginosa were treated with N,N'-dimethylformamide (DMF) or with ethylenediaminetetraacetate (EDTA). DMF solubilized 73% of the dry weight of the cell envelope, 76% of the protein, 78% of the carbohydrate, and 76% of the phosphorus. Electron microscopy showed that DMF caused extensive alterations in the appearance of the cell envelope with blebs and bleblike vesicles predominating. After incubation with EDTA, the cell envelopes appeared to have lost material, but still retained the cell-like morphology. Analysis of DMF-solubilized proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 16 protein bands. There were three major proteins that predominated, however, with molecular masses of 43,000 (protein A), 16,500 (protein B), and 72,000 daltons (protein C). Evidence is presented that protein A and protein B are glycoproteins. Gel electrophoresis of EDTA-solubilized material revealed that a number of proteins were released from the cell envelope. However, electrophoresis of an isolated protein-lipopolysaccharide complex released by EDTA showed that protein A and protein B were the major protein components of this complex. These data suggest that protein A and protein B are components of the outer cell wall membrane of P. aeruginosa. There is suggestive evidence that these proteins may play a role in maintaining the structural integrity of the cell envelope. Whether these proteins also have enzymatic activity could not be discerned from the present study, although it is possible that they may be associated with the terminal stages of lipopolysaccharide synthesis.