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The action of colicin E2 on supercoiled lambda DNA.II. Experiments in vitro
Biochemistry
|May 20, 1975
Summary
Colicin E2 exhibits DNase activity, causing DNA strand breaks in vitro. This enzymatic action is linked to its cell-killing properties in vivo, though contaminating nucleases are considered.
Area of Science:
- Molecular Biology
- Biochemistry
Background:
- Colicins are bacteriocins with diverse mechanisms of action.
- Colicin E2's cell-killing activity suggests enzymatic properties.
Purpose of the Study:
- To investigate the DNase activity of colicin E2.
- To correlate in vitro DNase activity with in vivo cell-killing effects.
Main Methods:
- Development of an in vitro system for colicin E2 activity testing.
- Incubation of purified colicin E2 with various DNA substrates (lambda phage, SV40, fd DNA).
- Analysis of DNA modifications using glycerol gradient fractionation.
Main Results:
- Purified colicin E2 induced single-strand scissions in supercoiled lambda phage DNA.
- Colicin E2 degraded superhelical SV40 DNA into open circles and fragments.
- Colicin E2 caused endonucleolytic breaks in single-stranded fd DNA.
Conclusions:
- Colicin E2 possesses intrinsic DNase activity.
- The in vitro DNase activity of colicin E2 is associated with its in vivo cell-killing mechanism.
- The potential contribution of contaminating nucleases requires further investigation.