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Seki K, Galindo JL, Karim AS, Jewett MC. A Cell-Free Gene Expression Platform for Discovering and Characterizing Stop Codon Suppressing tRNAs. ACS Chem Biol 2023; 18:1324-1334. [PMID: 37257197 DOI: 10.1021/acschembio.3c00051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Non-canonical amino acids (ncAAs) can be incorporated into peptides and proteins to create new properties and functions. Site-specific ncAA incorporation is typically enabled by orthogonal translation systems comprising a stop codon suppressing tRNA (typically UAG), an aminoacyl-tRNA synthetase, and an ncAA of interest. Unfortunately, methods to discover and characterize suppressor tRNAs are limited because of laborious and time-consuming workflows in living cells. In this work, we develop anEscherichia coli crude extract-based cell-free gene expression system to rapidly express and characterize functional suppressor tRNAs. Our approach co-expresses orthogonal tRNAs using endogenous machinery alongside a stop-codon containing superfolder green fluorescent protein (sfGFP) reporter, which can be used as a simple read-out for suppression. As a model, we evaluate the UAG and UAA suppressing activity of several orthogonal tRNAs. Then, we demonstrate that co-transcription of two mutually orthogonal tRNAs can direct the incorporation of two unique ncAAs within a single modified sfGFP. Finally, we show that the cell-free workflow can be used to discover putative UAG-suppressor tRNAs found in metagenomic data, which are nonspecifically recognized by endogenous aminoacyl-tRNA synthetases. We anticipate that our cell-free system will accelerate the development of orthogonal translation systems for synthetic biology.
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Affiliation(s)
- Kosuke Seki
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Joey L Galindo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Ashty S Karim
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
| | - Michael C Jewett
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208, United States
- Robert H. Lurie Comprehensive Cancer Center and Simpson Querrey Institute, Northwestern University, Chicago, Illinois 60611, United States
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