Abstract
Objective
To isolate and characterize the kinetics of variants of E. coli β-glucuronidase (GUS) having altered substrate specificity.
Results
Two small combinatorial libraries of E. coli GUS variants were constructed and screened for improved activities towards the substrate p-nitrophenyl-β-d-galactoside (pNP-gal). Nine of the most active variants were purified and their kinetic parameters were determined. These variants show up to 134-fold improved kcat/KM value towards pNP-gal compared to wild-type GUS, up to 9 × 108-fold shift in specificity from p-nitrophenyl-β-d-glucuronide (pNP-glu) to pNP-gal compared to wild-type, and 103-fold increase in specificity shift compared to a previously evolved GUS variant.
Conclusions
The kinetic data collected for nine new GUS variants is invaluable for training computational protein design models that better predict amino acid substitutions which improve activity of enzyme variants having altered substrate specificity.
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Acknowledgements
This project was supported by the National Science Foundation (CBET Award Number 0967062).
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Supplementary Table 1—List of primers used in this study.
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Li, Y., Wang, Z. & Cirino, P.C. Design and characterization of new β-glucuronidase active site variants with altered substrate specificity. Biotechnol Lett 40, 111–118 (2018). https://doi.org/10.1007/s10529-017-2447-6
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DOI: https://doi.org/10.1007/s10529-017-2447-6