Protein nanowires with tunable functionality and programmable self-assembly using sequence-controlled synthesis

Abstract

Advances in synthetic biology permit the genetic encoding of synthetic chemistries at monomeric precision, enabling the synthesis of programmable proteins with tunable properties. Bacterial pili serve as an attractive biomaterial for the development of engineered protein materials due to their ability to self-assemble into mechanically robust filaments. However, most biomaterials lack electronic functionality and atomic structures of putative conductive proteins are not known. Here, we engineer high electronic conductivity in pili produced by a genomically-recoded E. coli strain. Incorporation of tryptophan into pili increased conductivity of individual filaments >80-fold. Computationally-guided ordering of the pili into nanostructures increased conductivity 5-fold compared to unordered pili networks. Site-specific conjugation of pili with gold nanoparticles, facilitated by incorporating the nonstandard amino acid propargyloxy-phenylalanine, increased filament conductivity ~170-fold. This work demonstrates the sequence-defined production of highly-conductive protein nanowires and hybrid organic-inorganic biomaterials with genetically-programmable electronic functionalities not accessible in nature or through chemical-based synthesis.

A 300-fold conductivity increase in microbial cytochrome nanowires due to temperature-induced restructuring of hydrogen bonding networks

“…Our discovery also has implications in the rational design of protein nanowires ( 18 , 53 – 55 ). Our mechanistic studies of OmcS nanowires provide a framework for rational design of nanowire structures with tunable conductivity by modulating the redox potential of hemes and heme distortions by leveraging changes in the H-bonding.…”

Microbial biofilms as living photoconductors due to ultrafast electron transfer in cytochrome OmcS nanowires

“…Conductivity measurements on nanowires and biofilms were performed as described previously 62 . Connections to device electrodes were made with a probe station (MPI TS50) inside a Dark Box which formed a Faraday cage and also blocked background light.…”

Computational design and engineering of an Escherichia coli strain producing the nonstandard amino acid para-aminophenylalanine

“…Although short nsAA-bearing proteins, such as stapled peptides, have traditionally been generated via asymmetric synthesis methods ( Williams, 1999 ) and cell-free translation techniques exist for the production of larger proteins ( Hong et al., 2014 ), the ribosomal incorporation of nsAAs into the proteins of living cells greatly expands the scope and utility of nsAA-containing proteins. For instance, ribosomally synthesized nsAA-containing proteins can be incorporated into biocontainment strategies that limit the survival and propagation of engineered microbes to specified environments ( Mandell et al., 2015 ; Rovner et al., 2015 ), fluorescent proteins that serve as in vivo probes for enzymatic activities ( Xuan et al., 2017 ), and sequence-defined synthetic biomaterials containing multiple instances of nsAAs ( Amiram et al., 2015 ; Arranz-Gibert et al., 2018 ; Shapiro et al., 2022 ; Vanderschuren et al, 2022 ).…”