Metalloid resistance mechanisms in prokaryotes

Area of Science:

• Biochemistry
• Microbiology
• Molecular Biology

Background:

• Antibiotic and chemotherapeutic resistance is a significant global health issue.
• Active efflux is a common mechanism for microbial resistance to toxic compounds.
• Metal resistance systems, like the ars operon, serve as valuable models for understanding transport-related resistances.

Purpose of the Study:

• To review the biochemistry of the ars operon proteins from R-factor R773.
• To elucidate the novel regulatory and transport mechanisms conferring resistance to arsenicals and antimonials.

Main Methods:

• Focus on the biochemical characterization of proteins encoded by the ars operon.
• Analysis of transcriptional and allosteric regulation involving soft metal-thiol chemistry.
• Investigation of the transport system's substrate specificity and energy coupling mechanisms.

Main Results:

• The ars operon system exhibits dual regulation: transcriptional and allosteric, mediated by As(III) or Sb(III) interaction with cysteine thiols.
• Regulation utilizes high-affinity soft metal-thiol chemistry for rapid protein activation.
• The transport system employs low-affinity interactions with arsenic or antimony oxyanions, facilitating translocation across the cell membrane.
• The transporter can function as a secondary carrier using electrochemical energy or as an anion-translocating ATPase coupled to ATP hydrolysis.

Conclusions:

• The ars operon provides a robust model for studying resistance mechanisms, particularly active efflux.
• Novel regulatory and energy-coupling strategies highlight the adaptability of bacterial resistance systems.
• Understanding these mechanisms is crucial for developing strategies to combat antimicrobial and chemotherapeutic resistance.