Engineered TdT Polymerases for High-Temperature DNA Elongation
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Solution Overview
Problem
Existing terminal deoxynucleotidyl transferases (TdT) face challenges with secondary structure formation of single-stranded DNA substrates, leading to inhibited DNA elongation, and inefficient incorporation of 3' modified nucleotides, particularly at higher temperatures, which limits their use in template-independent DNA synthesis.
Innovation Solution
Engineered TdT polypeptides with specific amino acid substitutions, such as at positions S59, W200, M350, K156, and M316, exhibit increased thermostability, activity, and protein solubility, allowing efficient DNA synthesis at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wild-type TdT is used at higher temperatures to inhibit DNA secondary structures, then DNA elongation efficiency improves, but TdT activity and protein stability deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the optimal reaction temperature from 37°C to 50-60°C through protein engineering. This temperature parameter change allows the enzyme to maintain high activity while effectively inhibiting DNA secondary structure formation, thereby resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent replaces the mechanical/physical constraint of low-temperature operation with an engineered biochemical system that operates at elevated temperatures. Through amino acid substitutions and protein structure optimization, the TdT enzyme achieves thermostability while maintaining catalytic function, substituting the need for low-temperature mechanical control with a thermostable biochemical system.
2Adaptability or versatility
If 3' reversibly blocked nucleotides are used for template-independent DNA synthesis, then DNA synthesis capability improves, but incorporation efficiency deteriorates
Solution Approach 1:
The patent applies local quality by specifically optimizing the nucleotide binding site and active region of TdT to recognize and incorporate 3' modified nucleotides. Through targeted amino acid substitutions in the substrate binding region, the enzyme gains enhanced local affinity and catalytic efficiency for blocked nucleotides without compromising overall protein stability or function.
Solution Approach 2:
The patent employs preliminary action by pre-engineering the TdT enzyme with specific amino acid substitutions that optimize its ability to bind 3' modified nucleotides before the actual DNA synthesis reaction. This preliminary optimization of the enzyme's substrate recognition capability ensures high incorporation efficiency when blocked nucleotides are introduced into the reaction system.
3Productivity
If wild-type TdT is optimized to increase modified NTPs incorporation efficiency, then DNA synthesis efficiency improves, but protein stability deteriorates
Solution Approach 1:
The patent applies segmentation by separately optimizing different functional regions of the TdT enzyme. The substrate binding region is engineered to enhance modified NTP incorporation efficiency, while the core structural regions are maintained or optimized for protein stability. This segmented optimization approach allows independent improvement of catalytic efficiency without compromising structural integrity.
Solution Approach 2:
The patent uses parameter changes to simultaneously optimize multiple properties by adjusting amino acid compositions and protein structural parameters. Through systematic variation of temperature, pH, and amino acid sequence parameters, the engineered TdT achieves a new operational parameter set where both modified NTP incorporation efficiency and protein stability are enhanced compared to the wild-type enzyme.
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
The engineered TdT enzymes maintain activity and solubility at higher temperatures, effectively inhibiting DNA secondary structures and improving DNA synthesis efficiency, especially for longer fragments.
Implementation Method 1
Terminal deoxynucleotidyl transferase (TdT) is a template-independent DNA polymerase that elongates oligonucleotides in 5' to 3' direction
Implementation Method 2
to efficiently inhibit the formation of DNA secondary structures, reaction temperature should be raised to ~60°C
Data Source
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AI summary
The present invention provides an engineered terminal deoxynucleotidyl transferase (TdT) useful in template-independent polynucleotide synthesis, the terminal deoxynucleotidyl transferase having increased thermostability and/or increased TdT activity and/or increased protein solubility, as well as compositions comprising the said terminal deoxynucleotidyl transferase and methods comprising the use of said terminal deoxynucleotidyl transferase.