Genetically encoding phosphotyrosine and its nonhydrolyzable analog in bacteria

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Tyrosine phosphorylation is a crucial post-translational modification regulating cellular signaling and processes.
• Understanding the precise biological roles of tyrosine phosphorylation requires methods to study it at specific sites.

Purpose of the Study:

• To develop a novel method for site-specific incorporation of O-phosphotyrosine (pTyr) and its analog 4-phosphomethyl-L-phenylalanine (Pmp) into recombinant proteins.
• To establish an orthogonal aminoacyl-tRNA synthetase-tRNA pair for this purpose in Escherichia coli.
• To provide a tool for dissecting the biological functions of tyrosine phosphorylation at specific proteomic sites.

Main Methods:

• Utilized a propeptide strategy to enhance cellular uptake of pTyr and Pmp.
• Engineered an orthogonal aminoacyl-tRNA synthetase-tRNA pair for amber stop codon suppression.
• Employed X-ray crystallography to determine the structure of the engineered synthetase.
• Demonstrated the method by incorporating Pmp into a phosphorylation site and measuring binding affinities.

Main Results:

• Successfully established an orthogonal aminoacyl-tRNA synthetase-tRNA pair for site-specific pTyr and Pmp incorporation in E. coli.
• Achieved good yields of recombinant proteins containing the modified amino acids.
• Revealed a reconfigured substrate-binding site in the synthetase via X-ray structure analysis.
• Validated the utility of the method by analyzing protein-substrate interactions.

Conclusions:

• Developed a versatile recombinant tool for site-specific incorporation of tyrosine phosphorylation analogs.
• This method enables detailed investigation of tyrosine phosphorylation's role in specific cellular contexts.
• The structural insights into the synthetase provide a basis for further engineering efforts.