Giant single molecule chemistry events observed from a tetrachloroaurate(III) embedded Mycobacterium smegmatis porin A nanopore

Shuanghong Yan,Xiumei Xu,Jiao Cao,Wendong Jia,Hong-Yuan Chen,Yuqin Wang,Shuo Huang,Jinyue Zhang,Panke Zhang

doi:10.1038/s41467-019-13677-2

Shuanghong Yan, Xiumei Xu + Show 7 more

Open Access

https://doi.org/10.1038/s41467-019-13677-2

Copy DOI

Abstract

Biological nanopores are capable of resolving small analytes down to a monoatomic ion. In this research, tetrachloroaurate(III), a polyatomic ion, is discovered to bind to the methionine residue (M113) of a wild-type α-hemolysin by reversible Au(III)-thioether coordination. However, the cylindrical pore geometry of α-hemolysin generates shallow ionic binding events (~5–6 pA) and may have introduced other undesired interactions. Inspired by nanopore sequencing, a Mycobacterium smegmatis porin A (MspA) nanopore, which possesses a conical pore geometry, is mutated to bind tetrachloroaurate(III). Subsequently, further amplified blockage events (up to ~55 pA) are observed, which report the largest single ion binding event from a nanopore measurement. By taking the embedded Au(III) as an atomic bridge, the MspA nanopore is enabled to discriminate between different biothiols from single molecule readouts. These phenomena suggest that MspA is advantageous for single molecule chemistry investigations and has applications as a hybrid biological nanopore with atomic adaptors.

Highlights

Biological nanopores are capable of resolving small analytes down to a monoatomic ion
We have found that tetrachloroaurate(III) is an inhibitor of wild-type (WT) α-HL
Based on the known sulfur-gold (S-Au) coordination chemistry[24], methionine (M113)[25,26,27,28], which is in the proximity of the 1st restriction site of the pore[29] and is the only sulfur-containing amino acid within the inner surface of an α-HL monomer, could form a reversible interaction with freely translocating tetrachloroaurate (III) ions crossing the membrane

Summary

Introduction

Biological nanopores are capable of resolving small analytes down to a monoatomic ion. We have found that tetrachloroaurate(III) is an inhibitor of wild-type (WT) α-HL This results from a coordination interaction established between a Au (III) atom and the thioether residue within the pore restriction. The event amplitude, as generated from tetrachloroaurate(III) binding with MspA, is the largest that has been reported from an inorganic ion when sensed by a nanopore This suggests that MspA may be a superior template engineered as a nanoreactor to probe chemistry intermediates or kinetics in single molecule. As a proof of concept, the Au(III) embedded MspA nanopore discriminates between L-cysteine (Cys), L-homocysteine (Hcy) and Lglutathione (GSH) from direct single molecule readouts, which is a great challenge for fluorescence probe based imaging It suggests amino acid or peptide sensing strategies with gold embedded protein nanopores or other embedments as a variety of metalloporins

Methods

Results

Conclusion