Related Experiment Videos
Synthesis of E colicins in Escherichia coli
Abstract:
Mitomycin C treatment of Escherichia coli cells containing one of the ColE plasmids results in specific inhibition of chromosomal protein synthesis and a high rate of protein synthesis from about 35% of the plasmid genome, whereas similar treatment of plasmid-free cells has no measureable effect on protein synthesis. In the case of ColE2- and ColE3-containing cells, the antibiotic colicin protein (molecular weight about 78000) and two others (molecular weight about 11000 and 6000) are coordinately synthesized in the approximate molar ratio 1:4:1, while in ColE1-containing cells only the colicin protein is synthesized in large amounts. Partially purified colicin E2 isolated from the outer cell surface is associated with the two small proteins in the approximate molar ratio 1:1:1, indicating that not are they only synthesized coordinately but are released as a ternary complex.
Insights
Mitomycin C induces plasmid-specific protein synthesis in Escherichia coli. Colicin E2 and E3 plasmids lead to coordinated production of colicin and smaller proteins, forming a complex.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli (E. coli) is a model organism for studying bacterial genetics.
- Colicin plasmids encode bacteriocins, which are proteins toxic to other bacteria.
- The effect of Mitomycin C on plasmid gene expression in E. coli was not fully understood.
Purpose of the Study:
- To investigate the impact of Mitomycin C on protein synthesis in E. coli harboring ColE plasmids.
- To characterize the proteins synthesized from ColE1, ColE2, and ColE3 plasmids under Mitomycin C treatment.
- To determine the assembly and release mechanism of colicins and associated proteins.
Main Methods:
- Treatment of E. coli strains with Mitomycin C.
- Analysis of protein synthesis via gel electrophoresis.
- Isolation and purification of colicin E2 from the cell surface.
Main Results:
- Mitomycin C specifically inhibited chromosomal protein synthesis in plasmid-containing E. coli.
- ColE2 and ColE3 plasmids directed the coordinate synthesis of colicin protein and two smaller proteins in specific molar ratios.
- Colicin E1 plasmid primarily synthesized only the colicin protein.
- Partially purified colicin E2 was found to be a ternary complex with the two smaller proteins in a 1:1:1 molar ratio.
Conclusions:
- Mitomycin C induces a specific pattern of protein synthesis from ColE plasmids in E. coli.
- Colicin E2 and E3 plasmids encode proteins that are coordinately synthesized and released as a functional complex.
- The findings provide insights into plasmid gene regulation and protein complex formation in bacteria.