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An Economical Method for Cell-Free Protein Synthesis using Glucose and Nucleoside Monophosphates

Authors

  • Kara A. Calhoun,

    1. Department of Chemical Engineering, Stanford University, Stanford, California 94305–5025
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  • James R. Swartz

    Corresponding author
    1. Department of Chemical Engineering, Stanford University, Stanford, California 94305–5025
    2. Department of Bioengineering, Stanford University, Stanford, California 94305–5025
    • Department of Chemical Engineering, Stanford University, Stanford, California 94305–5025. Ph: (650) 723–5398. Fax: (650) 725–0555
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Abstract

Cell-free protein synthesis reactions have not been seriously considered as a viable method for commercial protein production mainly because of high reagent costs and a lack of scalable technologies. Here we address the first issue by presenting a cell-free protein synthesis system with comparable protein yields that removes the most expensive substrates and lowers the cell-free reagent cost by over 75% (excluding extract, polymerase, and plasmid) while maintaining high energy levels. This system uses glucose as the energy source and nucleoside monophosphates (NMPs) in place of nucleoside triphosphates (NTPs) as the nucleotide source. High levels of nucleoside triphosphates are generated from the monophosphates within 20 min, and the subsequent energy charge is similar in reactions beginning with either NTPs or NMPs. Furthermore, significant levels (>0.2 mM) of all NTPs are still available at the end of a 3-h incubation, and the total nucleotide pool is stable throughout the reaction. The glucose/NMP reaction was scaled up to milliliter scale using a thin film approach. Significant yields of active protein were observed for two proteins of vastly different size: chloramphenicol acetyl transferase (CAT, 25 kDa) and β-galactosidase (472 kDa). The glucose/NMP cell-free reaction system dramatically reduces reagent costs while supplying high protein yields.

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