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Outer membrane protein G: Engineering a quiet pore for biosensing.

Min Chen1, Syma Khalid, Mark S P Sansom

  • 1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom.

Proceedings of the National Academy of Sciences of the United States of America
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Researchers stabilized the OmpG bacterial porin by reducing its gating activity through mutagenesis. This engineered porin enables sensitive single-molecule detection of analytes like adenosine diphosphate for stochastic sensing applications.

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Area of Science:

  • Biophysics
  • Biochemistry
  • Nanotechnology

Background:

  • Bacterial outer membrane porins, like OmpG, possess a stable beta-barrel structure suitable for single-molecule detection.
  • OmpG's monomeric nature facilitates mutagenesis for pore modification, but its spontaneous gating hinders analyte detection.
  • Transient current blockades from OmpG gating interfere with reliable single-molecule sensing.

Purpose of the Study:

  • To eliminate spontaneous gating activity in the OmpG porin.
  • To enhance the stability of the OmpG porin's open conformation for improved sensing.
  • To demonstrate the utility of a stabilized OmpG mutant in stochastic sensing applications.

Main Methods:

  • Molecular dynamics simulations were employed to identify OmpG regions responsible for gating.
  • Site-directed mutagenesis was used to introduce stabilizing mutations, including a disulfide bond and residue deletion.
  • Single-channel recordings and single-molecule detection assays were performed.

Main Results:

  • Molecular dynamics simulations pinpointed key regions involved in OmpG gating.
  • Two mutations, a disulfide bond in loop 6 and deletion of D215, significantly stabilized the OmpG pore.
  • The engineered OmpG mutant showed a 95% reduction in gating activity.
  • The stabilized OmpG mutant successfully detected adenosine diphosphate at the single-molecule level.

Conclusions:

  • Stabilizing mutations effectively eliminate spontaneous gating in OmpG porins.
  • The engineered OmpG mutant is a promising platform for single-molecule stochastic sensing.
  • This work advances the development of porin-based biosensors for various analytes.