title: Cross-linking of the proteins in the outer membrane of Escherichia coli.
abstract: 1. The organization of the proteins in the outer membrane of Escherichia coli was examined by the use of cross-linking agents and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of protein A-peptidoglycan complexes with dithiobis(succinimidyl propionate) or glutaraldehyde produced the dimer, trimer, and higher oligomers of protein A. Both forms of this protein, proteins A1 and A2, produced similar cross-linking products. No cross-linking of protein A to the peptidoglycan was detected. 2. The proteins of the isolated outer membrane varied in their ease of cross-linking. The heat-modifiable protein, protein B, was readily cross-linked to give high molecular weight oligomers, while protein A formed mainly the dimer and trimer under the same conditions. The pronase resistant fragment, protein Bp, derived from protein B was not readily cross-linked. No linkage of protein A to protein B was detected. 3. Cross-linking of cell wall preparations, consisting of the outer membrane and peptidoglycan, showed that protein B and the free form of the lipoprotein, protein F, could be linked to the peptidoglycan. A dimer of protein F, and protein F linked to protein B, were detected. 4. These results suggest that specific protein-protein interactions occur in the outer membrane.
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D004926:Escherichia coli / Q000032:analysis*; D008074:Lipoproteins / Q000032:analysis; D008565:Membrane Proteins / Q000032:analysis*; D010457:Peptidoglycan / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D010457:Peptidoglycan