Synthetic Biological Protein Nanowires with High Conductivity

Abstract

Genetic modification to add tryptophan to PilA, the monomer for the electrically conductive pili of Geobacter sulfurreducens, yields conductive protein filaments 2000‐fold more conductive than the wild‐type pili while cutting the diameter in half to 1.5 nm.

Electrically Conductive Pili from Pilin Genes of Phylogenetically Diverse Microorganisms

“…e-Pili are a potential source of 'green' electronic materials that can be sustainably mass-produced with renewable feedstocks without toxic components in the final product (Adhikari et al 2016, Tan et al 2016a, Tan et al 2017. The e-pili described here greatly expand the options for starting materials and the screening method described will facilitate searching the microbial world, including the metagenomes of uncultured microorganisms, for additional conductive materials.…”

“…Aromatic amino acids are key components in electron transfer along the length of G. sulfurreducens e-pili (Adhikari et al 2016, Lampa-Pastirk et al 2016, Tan et al 2016a, Tan et al 2017, Vargas et al 2013. There is debate whether the aromatic amino acids contribute to a traditional electron-hopping electron transport mechanism or whether over-lapping π-π orbitals of the aromatics confer a metallic-like conductivity similar to that observed in synthetic conducting polymers (Lampa-Pastirk et al 2016, Lovley and Malvankar 2015, Vargas et al 2013.…”

“…It is possible to screen pilin genes to determine if they have the potential to yield pilin proteins that can assemble into e-pili by heterologously expressing the pilin gene of interest in G. sulfurreducens in place of the native G. sulfurreducens pilin gene (Liu et al 2014, Tan et al 2016a, Tan et al 2016b, Tan et al 2017, Vargas et al 2013. Only if the pilin gene yields e-pili is G. sulfurreducens then capable of producing high current densities on graphite electrodes.…”

Microbial nanowires: an electrifying tale

“…Furthermore, Leung et al (2011) characterized S. oneidensis MNWs and showed that they have enough mechanical strength (Young's modulus~1 GPa) to be used as a building block for construction of electronic devices. The MNWs can be modified using genetic and protein engineering, so different ligands (metals) can be attached to it which may help to modulate its electric behaviour (Lovley et al, 2009) or can increase its electrical conductivity significantly (Tan et al, 2016). In this direction, MNWs in G. sulfurreducens have been modified to have better conductive and adhesive properties (Reguera et al, 2014).…”

“…In this direction, MNWs in G. sulfurreducens have been modified to have better conductive and adhesive properties (Reguera et al, 2014). A recent study by Tan et al (2016) has shown that, in G. sulfurreducens MNWs, replacing C-terminal phenylalanine and tyrosine of PilA with tryptophan decreases its diameter by half and increases its conductivity by~2000-fold. MNWs may also be used in bionanosensors (Lovley et al, 2009); however, no such studies have been reported yet.…”