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A Facile Protocol to Generate Site-Specifically Acetylated Proteins in Escherichia Coli
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Polyspecific pyrrolysyl-tRNA synthetases from directed evolution.

Li-Tao Guo1, Yane-Shih Wang1, Akiyoshi Nakamura2

  • 1Departments of Molecular Biophysics & Biochemistry and.

Proceedings of the National Academy of Sciences of the United States of America
|November 12, 2014
PubMed
Summary
This summary is machine-generated.

Pyrrolysyl-tRNA synthetase (PylRS) variants enable genetic code expansion by incorporating noncanonical amino acids (ncAAs). New research reveals structural insights into enzyme polyspecificity, crucial for advancing synthetic biology and protein engineering.

Keywords:
aminoacyl-tRNA synthetasegenetic codegenetic selectionposttranslational modificationsynthetic biology

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Area of Science:

  • Biochemistry
  • Synthetic Biology
  • Molecular Biology

Background:

  • Pyrrolysyl-tRNA synthetase (PylRS) and its tRNA(Pyl) are key tools for genetic code innovation.
  • Enzyme variants allow the incorporation of over 100 noncanonical amino acids (ncAAs) into proteins.
  • Previous PylRS variants were selected for specific amino acid acylation, like N(ε)-acetyl-Lys (AcK).

Purpose of the Study:

  • To investigate the molecular basis of polyspecificity in N(ε)-acetyl-lysyl-tRNA synthetase (AcKRS).
  • To analyze an enhanced PylRS variant, iodo-phenylalanyl-tRNA synthetase (IFRS), for activity and substrate promiscuity.
  • To understand how enzyme specificity impacts genetic code expansion.

Main Methods:

  • Biochemical assays to determine enzyme activity and substrate specificity.
  • Structural biology techniques to elucidate enzyme-tRNA-amino acid interactions.
  • Directed evolution to generate and select PylRS variants with altered properties.

Main Results:

  • AcKRS exhibits polyspecificity, being more efficient with Phenylalanine derivatives than its intended substrate AcK.
  • IFRS, a directed evolution product, shows enhanced activity and promiscuity across 313 tested ncAAs.
  • Structural and biochemical data reveal distinct binding modes for different ncAAs in IFRS.
  • In vivo selections may not yield optimally specific tRNA synthetases.

Conclusions:

  • The study reveals the molecular underpinnings of polyspecificity in tRNA synthetases.
  • Findings suggest that translation fidelity is a critical consideration for further genetic code expansion.
  • Optimizing enzyme specificity is essential for the precise incorporation of diverse ncAAs in synthetic biology applications.