Thermostable TdT Variant for 3'-Modified Nucleotide Incorporation
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Solution Overview
Problem
Wild-type terminal deoxynucleotidyl transferase (TdT) is not optimized for incorporating 3′ modified nucleotides and is marginally stable, making it unsuitable for efficient enzymatic oligonucleotide and gene synthesis, particularly at higher temperatures where DNA secondary structures inhibit activity.
Innovation Solution
A recombinant TdT variant with specific amino acid substitutions at positions equivalent to Glu191, Lys193, Glu194, Asp242, Lys287, Phe296, Met299, Thr342, and His421, which enhances thermostability and allows efficient incorporation of 3′-modified nucleotides, maintaining catalytic activity at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wild-type TdT is used for incorporation of 3′ modified nucleotides, then the enzyme can catalyze template free incorporation of arbitrary nucleotides, but the enzyme is not optimized for 3′ modified nucleotide incorporation and is marginally stable
Solution Approach 1:
The patent applies parameter changes by introducing specific amino acid substitutions at positions Glu191, Lys193, Glu194, Asp242, Lys287, Phe296, Met299, Thr342, and His421 in the TdT enzyme sequence. These parameter changes in the protein structure enable the enzyme to achieve both thermostability and optimized activity for incorporating 3′ modified nucleotides, resolving the contradiction between stability and functional optimization.
2Adaptability or versatility
If mutations are introduced to enable 3′ block incorporation, then the ability to incorporate 3′ modified nucleotides is improved, but thermostability decreases due to marginal stability of wild-type TdT
Solution Approach 1:
The patent applies preliminary action by first establishing a thermostable TdT variant through specific amino acid substitutions before introducing mutations for 3′ block incorporation capability. This preliminary stabilization of the enzyme structure provides a robust foundation that can subsequently accommodate functional mutations without compromising thermostability, thereby resolving the contradiction between stability and functional enhancement.
3Temperature
If wild-type TdT is used at higher temperatures, then DNA secondary structure formation is reduced, but the enzyme activity is inhibited by these secondary structures
Solution Approach 1:
The patent applies parameter changes by creating a thermostable TdT variant through specific amino acid substitutions that enable the enzyme to maintain structural integrity and catalytic activity at elevated temperatures. This allows the enzyme to operate effectively at temperatures where DNA secondary structures are minimized, thereby resolving the contradiction between temperature and productivity.
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 recombinant TdT variant exhibits increased thermostability, enabling efficient incorporation of 3′-modified nucleotides and maintaining activity at temperatures up to 58°C, overcoming the limitations of wild-type TdT in synthesizing long DNA molecules and minimizing DNA secondary structure formation.
Implementation Method 1
Terminal deoxynucleotidyl transferase (TdT) catalyzes template free incorporation of arbitrary nucleotides onto single-stranded DNA
Data Source
AI summary
Disclosed herein include recombinant terminal deoxynucleotidyl transferases (TdTs). In some embodiments, the recombinant TdT comprises an amino acid sequence that is at least 80% identical to a bovine TdT, wherein the recombinant TdT comprises one or more amino acid substitution mutations at one or more positions functionally equivalent to Glu191, Lys193, Glu194, Asp242, Lys287, Phe296, Met299, Thr342, and His421 in the bovine TdT.