Isolation of labeled lipoprotein from Escherichia coli and Proteus mirabilis after incubation with [14C]penicillin.

[14C]penicillin binding experiments and membrane analysis were carried out with cell envelope preparations from Escherichia coli and Proteus mirabilis. After incubation with [14C]penicillin G labeled free lipoprotein could be identified. The analysis of the isolated lipoprotein by SDS polyacrylamide gel electrophoresis indicates that there is only one protein with an apparent molecular weight of 7000. The amino acid composition of isolated labeled free lipoprotein from E. coli was identical to the lipoprotein already found in E. coli. It is a point of interest that the amino acid composition of the isolated labeled free lipoprotein from P. mirabilis D 52 differs from that found in other mutants of this strain. The free form of lipoprotein from P. mirabilis D 52 is composed of 61 amino acids and has glycine, phenylalanine and proline as specific components.