Study of envelope proteins in E. coli cet and recA mutants by SDS acrylamide gel electrophoresis

Changes in membrane proteins of Escherichia coli K12 mediated by bacteriophage IKe-specific plasmids

At least 3 minor proteins have been detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the unseparated (31 000 daltons) and inner membranes (53 000 and 86 000 daltons) of a non-piliated strain of E. coli K12 bearing the phage IKe-specific resistance plasmid RM98 (Tra+); these proteins are lacking in its Tra- derivative and in the plasmidless host. In contrast, in another K12 host carrying each of different IKe-specific colicinogenic factors, an extra 30 000 dalton protein is observed in the outer membranes; a number of minor proteins seen in the inner membranes appear to be different from those observed in the RM98+ strain. The evidence suggests that the 30 000-31 000 dalton protein is transfer function specific.

Detection of a protein, similar to the sex pilus subunit, in the outer membrane of Escherichia coli cells carrying a derepressed F-like R factor

The outer membranes of Escherichia coli K-12 cells carrying a derepressed F-like R factor contain about 7 times 10-4 molecules per cell of a protein similar to the subunit of the sex pili specified by the R factor. This protein pool is absent in cells carrying the repressed variant of the R factor. The size of the pool is about one-half of the amount of protein incorporated into mature sex pili at the peak of production and is independent of the phase of growth of the culture. The molecular weight of the protein in the pool and of the subunit of the sex pili specified by the cells is 12,500 plus or minus 600.

Sodium dodecyl sulfate in protein chemistry

This review summarizes in a brief manner the main aspects of the application of sodium dodecyl sulfate (SDS) to protein chemistry. The principal problems of SDS-polyacrylamide gel electrophoresis are described, as well as the anomalous behavior of protein-SDS complexes and the inactivation of enzymes due to variable binding of SDS to the polypeptides studied. The particular value of SDS in elucidating the protein composition of biological membranes and in membrane-reconstitution experiments is discussed.

Proteins of the inner membrane of Escherichia coli: changes in composition associated with anaerobic growth and fumarate reductase amber mutation

The inner membrane fractions of Escherichia coli grown anaerobically and aerobically were isolated, and their proteins were compared by electrophoresis in polyacrylamide gels. To maximimize the differences between the preparations, the anaerobic cultures were grown on complex medium with added glucose, but glucose was omitted from the aerobic cultures to prevent catabolite repression. The pattern of bands in the two types of preparation differed considerably, and changes in approximately 20 components were observed. In particular, the band identified as succinate dehydrogenase in aerobic preparations was greatly reduced in anaerobic preparations. Mutants lacking fumarate reductase were isolated, and inner membrane preparations of an frd amber mutant were deficient in a major component of 75,000 daltons and possibly a minor one of 87,500 daltons. The former was also present in greater amounts in anaerobic preparations and could represent a fumarate reductase subunit.

Proteins of the inner membrane of Escherichia coli: identification of succinate dehydrogenase by polyacrylamide gel electrophoresis with sdh amber mutants

The inner or cytoplasmic membrane fraction of the cell envelope of Escherichia coli was isolated by isopycnic centrifugation on sucrose gradients. The membrane proteins were analyzed by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels (8.5%), and up to 56 bands were resolved. Different preparations gave very similar patterns of proteins. Succinate dehydrogenase mutants (sdh) were isolated which could not grow on succinate minimal medium, although growth on fumarate was unimpaired. The protein patterns of inner membrane preparations from sdh amber mutants were compared with the wild type, and one major band was greatly reduced in the mutants. This component, which represented approximately 5% of the inner membrane protein, was restored by introducing an amber suppressor gene (supU), which also restored the Sdh(+) phenotype. The band corresponded to a protein with a molecular weight of 67,000 daltons, which is close to that for the large subunits of the succinate dehydrogenases of Rhodospirillum rubrum and beef heart mitochondria.

Aeruginocin tolerant mutants of Pseudomonas aeruginosa

Mutants ofPseudomonas aeruginosatolerant to the action of trypsinsensitive aeruginocins can be readily isolated. They are found to be heterogeneous for a range of phenotypic characteristics (including the pattern of membrane protein components in polyacrylamide gel electrophoresis), response to bacteriophages (including both plaque formation and the ability to be lysogenized), sensitivity to various toxic agents, colonial morphology, and cellular morphology. The nature of these changes strongly supports the view that the mutants examined have undergone alteration in membrane structure. A limited genetic analysis indicates that at least two chromosomal regions are involved.