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Genetically programmed chiral organoborane synthesis

Kan, S. B. Jennifer and Huang, Xiongyi and Gumulya, Yosephine and Chen, Kai and Arnold, Frances H. (2017) Genetically programmed chiral organoborane synthesis. Nature, 552 (7683). pp. 132-136. ISSN 0028-0836. http://resolver.caltech.edu/CaltechAUTHORS:20171027-110146134

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Abstract

Recent advances in enzyme engineering and design have expanded nature’s catalytic repertoire to functions that are new to biology. However, only a subset of these engineered enzymes can function in living systems. Finding enzymatic pathways that form chemical bonds that are not found in biology is particularly difficult in the cellular environment, as this depends on the discovery not only of new enzyme activities, but also of reagents that are both sufficiently reactive for the desired transformation and stable in vivo. Here we report the discovery, evolution and generalization of a fully genetically encoded platform for producing chiral organoboranes in bacteria. Escherichia coli cells harbouring wild-type cytochrome c from Rhodothermus marinus8 (Rma cyt c) were found to form carbon–boron bonds in the presence of borane–Lewis base complexes, through carbene insertion into boron–hydrogen bonds. Directed evolution of Rma cyt c in the bacterial catalyst provided access to 16 novel chiral organoboranes. The catalyst is suitable for gram-scale biosynthesis, providing up to 15,300 turnovers, a turnover frequency of 6,100 h^(–1), a 99:1 enantiomeric ratio and 100% chemoselectivity. The enantiopreference of the biocatalyst could also be tuned to provide either enantiomer of the organoborane products. Evolved in the context of whole-cell catalysts, the proteins were more active in the whole-cell system than in purified forms. This study establishes a DNA-encoded and readily engineered bacterial platform for borylation; engineering can be accomplished at a pace that rivals the development of chemical synthetic methods, with the ability to achieve turnovers that are two orders of magnitude (over 400-fold) greater than those of known chiral catalysts for the same class of transformation. This tunable method for manipulating boron in cells could expand the scope of boron chemistry in living systems.


Item Type:Article
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https://doi.org/10.1038/nature24996DOIArticle
https://www.nature.com/articles/nature24996PublisherArticle
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ORCID:
AuthorORCID
Arnold, Frances H.0000-0002-4027-364X
Additional Information:© 2017 Macmillan Publishers Limited, part of Springer Nature. Received: 22 July 2017; Accepted: 02 November 2017; Published online: 29 November 2017. This work was supported in part by the National Science Foundation, Office of Chemical, Bioengineering, Environmental and Transport Systems SusChEM Initiative (grant CBET-1403077), the Gordon and Betty Moore Foundation through grant GBMF2809 to the Caltech Programmable Molecular Technology Initiative, and the Jacobs Institute for Molecular Engineering for Medicine at Caltech. X.H. is supported by a Ruth L. Kirschstein National Institutes of Health Postdoctoral Fellowship (F32GM125231). We thank O. F. Brandenberg, S. Brinkmann-Chen, T. Hashimoto, R. D. Lewis, and D. K. Romney for discussions and/or comments on the manuscript, and N. W. Goldberg and A. Zutshi for experimental assistance. We are grateful to S. Virgil, N. Torian, M. K. Takase and L. Henling for analytical support, and H. Gray for providing the pEC86 plasmid. Author Contributions: S.B.J.K. and X.H. designed the research with guidance from F.H.A. S.B.J.K., X.H., Y.G. and K.C. performed the experiments and analysed the data. S.B.J.K., X.H. and F.H.A. wrote the manuscript with input from all authors. Competing interests: A provisional patent application has been filed through the California Institute of Technology based on the results presented here.
Funders:
Funding AgencyGrant Number
NSFCBET-1403077
Gordon and Betty Moore FoundationGBMF2809
Jacobs Institute for Molecular Engineering for MedicineUNSPECIFIED
NIH Postdoctoral FellowshipF32GM125231
Record Number:CaltechAUTHORS:20171027-110146134
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171027-110146134
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82732
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:29 Nov 2017 19:18
Last Modified:15 Dec 2017 23:30

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