Detergent headgroups control TolC folding in vitro

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• TolC is the outer membrane protein of the Escherichia coli efflux pump system, mediating antibiotic expulsion.
• Overexpression of efflux pumps in bacterial pathogens reduces antibiotic susceptibility.
• Characterizing membrane proteins like TolC is vital for understanding efflux mechanisms and developing new therapeutics.

Purpose of the Study:

• To investigate the in vitro folding of TolC into its functional trimeric state from inclusion bodies.
• To determine the effect of detergent micelle headgroup composition on TolC folding.
• To identify optimal conditions for producing active TolC for further studies.

Main Methods:

• Recombinant TolC protein was produced and purified from inclusion bodies.
• In vitro refolding experiments were conducted using various detergents with different headgroup compositions and alkyl chain lengths.
• The oligomeric state and functional folding of refolded TolC were assessed using biophysical techniques.

Main Results:

• The in vitro folding of TolC into its functional trimeric form is critically dependent on the detergent micelle headgroup composition.
• Nonionic detergents promote the formation of functional trimeric TolC.
• Zwitterionic detergents lead to the formation of non-native, oligomeric TolC structures, while shorter alkyl chain nonionic detergents enhance folding.

Conclusions:

• Detergent choice is a key factor in achieving successful in vitro refolding of the trimeric TolC protein.
• Understanding these detergent-mediated folding pathways is essential for structural and biophysical characterization of TolC.
• Further research is needed to explore the impact of lipid headgroup charges on TolC folding in biological membranes.