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Thiols, recA induction and radiosensitivity in Escherichia coli
M Naslund1, B Anderstam, F Granath
1Department of Radiobiology, Stockholm University, Sweden.
International Journal of Radiation Biology
|January 1, 1996
Summary
2-mercaptoethylamine (MEA) inhibits RecA gene induction in E. coli, but cysteine (Cys) counteracts this effect. MEA also increases radio-resistance, an effect reversed by Cys, independent of DNA repair proficiency.
Area of Science:
- Microbiology
- Molecular Biology
- Radiation Biology
Background:
- RecA protein synthesis is induced by DNA-damaging agents like gamma radiation, UV radiation, and hydroxyurea.
- This induction is crucial for bacterial DNA repair mechanisms.
Purpose of the Study:
- To investigate the effect of 2-mercaptoethylamine (MEA) and cysteine (Cys) on RecA gene induction in Escherichia coli.
- To determine if MEA and Cys influence bacterial radio-resistance and DNA repair pathways.
Main Methods:
- Utilized recA-lacZ fusion strains of E. coli to monitor RecA gene product synthesis.
- Administered inducing agents (gamma radiation, UV radiation, hydroxyurea) with or without MEA and Cys.
- Assessed bacterial radio-resistance and excision-repair proficiency (uvrA+ and uvrA- strains).
Main Results:
- MEA significantly inhibited RecA induction by all tested agents.
- Cysteine counteracted the inhibitory effect of MEA on RecA induction.
- MEA treatment increased radio-resistance in E. coli, an effect reversed by Cys.
- These effects were independent of the bacterial excision-repair system (uvrA status).
- MEA and Cys did not increase intracellular thiol concentrations but elevated glutathione levels.
Conclusions:
- MEA acts as a competitive inhibitor of cysteine's role in RecA induction.
- MEA enhances bacterial radio-resistance through a mechanism modulated by cysteine, independent of excision repair.
- The observed effects are likely mediated by pathways involving glutathione, not direct thiol concentration changes.