Interactions of membrane lipoproteins with the murein sacculus of Escherichia coli as shown by chemical crosslinking studies of intact cells.

Proteins that were closely associated with murein in intact cells of Escherichia coli were studied by treating [3H]leucine and [3H]palmitate-labeled cells with the chemical crosslinking reagent dithiobis(succinimidylpropionate). Murein was purified and crosslinked peptides were released from the murein by treatment with beta-mercaptoethanol. Nine murein-associated [3H]leucine-labeled peptides were identified. Five of the nine peptides were lipoproteins, based on labeling with [3H]palmitate, protease sensitivity and gel electrophoretic correspondence to membrane lipoproteins present in uncrosslinked cell envelope preparations. The results suggest that these membrane lipoproteins may play a significant role in the structural integration of the murein and membrane layers of the cell envelope.