Mutant Elongation Factor Protects Phosphoseryl-tRNA for Stable Protein Incorporation
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Solution Overview
Problem
Current methods for site-specific phosphorylation of proteins are inefficient and unstable, particularly in recombinant proteins expressed in bacterial or fungal systems, which do not phosphorylate proteins like mammalian cells, making it difficult to achieve targeted and stable incorporation of phosphoserine.
Innovation Solution
The use of mutant elongation factor proteins (EF-Sep) in conjunction with phosphoseryl-tRNA synthetase (SepRS) and phosphoseryl-tRNA (tRNASep) to specifically incorporate phosphoserine into proteins by aminoacylating tRNASep with O-phosphoserine and utilizing EF-Sep to protect it from deacylation and catalyze its transfer onto the polypeptide, allowing for site-specific phosphorylation indistinguishable from kinase-mediated phosphorylation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphorylation methods are used in bacterial or fungal expression systems, then protein expression is achieved, but site-specific phosphorylation is inefficient and unstable
Solution Approach 1:
The patent introduces an orthogonal tRNA/Synthetase pair as an intermediary system to achieve site-specific phosphoserine incorporation. The phosphoseryl-tRNA synthetase (SepRS) specifically recognizes phosphoserine and charges tRNASep, creating a dedicated pathway that bypasses the limitations of conventional phosphorylation methods in bacterial systems. This intermediary system enables reliable and efficient site-specific phosphorylation by mediating the specific incorporation of phosphoserine at target sites.
2Reliability
If mutant elongation factor proteins are used to protect phosphoseryl-tRNA from deacylation, then stability of phosphoserine incorporation is improved, but the complexity of the expression system increases
Solution Approach 1:
The patent segments the phosphorylation function into distinct modular components: (1) phosphoseryl-tRNA synthetase for specific phosphoserine recognition and charging, (2) mutant elongation factor for protection and delivery, and (3) phosphoseryl-tRNA for targeted incorporation. This segmentation allows each component to be independently optimized and controlled, improving overall stability while managing system complexity through functional modularity.
Solution Approach 2:
The mutant elongation factor is engineered in advance with specific mutations that pre-confer protection against deacylation. This preliminary action of pre-modifying the elongation factor ensures that once the phosphoseryl-tRNA is formed, it is immediately protected during translation, eliminating the need for additional protective measures during the expression process.
3Manufacturing precision
If site-specific phosphorylation is achieved through conventional methods, then some phosphorylation occurs, but the phosphorylation is not stable and cannot be reliably reproduced
Solution Approach 1:
The patent applies local quality by creating a highly specific local environment for phosphoserine incorporation through the orthogonal tRNA/Synthetase pair. The phosphoseryl-tRNA synthetase exhibits high specificity for phosphoserine at the aminoacylation site, and the mutant elongation factor provides localized protection at the translation site. This localized specificity ensures precise and reproducible site-specific phosphorylation without affecting other regions of the protein.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the stable and efficient incorporation of phosphoserine into proteins, facilitating their use in studying kinases, phosphatases, and signal transduction pathways, as well as in drug discovery and therapeutic agent development, with applications in both in vivo and in vitro systems.
Implementation Method 1
SepRS preferentially aminoacylates tRNASep with O-phosphoserine
Implementation Method 2
EF-Sep proteins can bind Sep-tRNASep and protect Sep-tRNASep from deacylation and catalyze the covalent transfer of the phosphoserine amino acid onto the polypeptide
Data Source
AI summary
Nucleic acids encoding mutant elongation factor proteins (EF-Sep), phosphoseryl-tRNA synthetase (SepRS), and phosphoseryl-tRNA (tRNASep) and methods of use in site specific incorporation of phosphoserine into a protein or polypeptide are described. Mutant EF-Sep proteins are disclosed that bind Sep-tRNASep and protect Sep-tRNASep from deacylation. In a preferred embodiment the nucleic acids are on vectors and are expressed in cells such as bacterial cells, archeaebacterial cells, and eukaryotic cells. Proteins or polypeptides containing phosphoserine produced by the methods described herein can be used for a variety of applications such as research, antibody production, protein array manufacture and development of cell-based screens for new drug discovery.