ArsP: a methylarsenite efflux permease
Jian Chen1, Mahendra Madegowda1, Hiranmoy Bhattacharjee1
1Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 33199, USA.
Molecular Microbiology
|August 4, 2015
Summary
Trivalent organoarsenicals, like methylarsenite and roxarsone, are highly toxic. The bacterial permease ArsP specifically exports these toxic compounds, representing the first identified efflux system for trivalent organoarsenicals.
Area of Science:
- Environmental microbiology
- Toxicology
- Biochemistry
Background:
- Trivalent organoarsenicals exhibit higher toxicity than pentavalent or inorganic forms.
- Microbial methylation converts inorganic arsenite to toxic methylarsenite.
- Herbicides like MSMA and feed additives like roxarsone can be converted to toxic trivalent forms in vivo.
Purpose of the Study:
- To investigate the function of Campylobacter jejuni ArsP in the transport of organoarsenicals.
- To determine the specificity of ArsP for different arsenic species.
- To elucidate the mechanism of ArsP-mediated resistance.
Main Methods:
- Expression of C. jejuni arsP in Escherichia coli.
- Assessing resistance to various arsenic compounds in E. coli expressing arsP.
- Utilizing everted membrane vesicles to study transport activity.
- Investigating the role of conserved cysteine residues in ArsP function.
Main Results:
- E. coli expressing arsP showed resistance to methylarsenite (MAs(III)) and roxarsone (Rox(III)).
- ArsP-mediated resistance was specific for trivalent organoarsenicals, not inorganic or pentavalent forms.
- Membrane vesicles demonstrated active efflux of MAs(III) and Rox(III) via ArsP.
- Conserved cysteine residues in ArsP are crucial for its transport activity.
Conclusions:
- ArsP is the first identified efflux system specifically for trivalent organoarsenicals.
- ArsP confers resistance by actively exporting toxic trivalent organoarsenicals from the cell.
- Understanding ArsP function is critical for mitigating arsenic toxicity in microbial systems.
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