Modified TdT Enzymes for Template-Independent DNA Synthesis
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Solution Overview
Problem
Current DNA synthesis technologies face challenges in producing DNA strands longer than 200 nucleotides due to inefficiencies in nucleotide coupling, requiring laborious and costly methods like 'synthesize and stitch' techniques, and lack of suitable enzymes for template-independent single-stranded DNA synthesis.
Innovation Solution
Modified terminal deoxynucleotidyl transferase (TdT) enzymes with enhanced catalytic activity and temperature stability, incorporating specific amino acid modifications such as E456G, R457S, and N473G, enable efficient incorporation of 3′-O-reversibly terminated nucleotides for de novo single-stranded DNA synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synthetic chemistry (phosphoramidite technology) is used to couple nucleotides one at a time, then DNA can be synthesized, but the process becomes laborious and mathematically impossible to synthesize DNA longer than 200 nucleotides in acceptable yields
Solution Approach 1:
The patent replaces the chemical synthesis mechanism (phosphoramidite technology) with an enzymatic mechanism (modified TdT enzyme). This substitution enables template-independent DNA synthesis beyond the 200 nucleotide limit by using the enzyme's catalytic activity to add nucleotides to the 3' end of DNA strands, fundamentally changing how DNA is synthesized from a chemical process to a biological catalytic process.
Solution Approach 2:
The patent modifies the TdT enzyme through specific amino acid changes (E456G, R457S, N473G) to alter its catalytic parameters and substrate specificity. These parameter changes enable the enzyme to work at higher temperatures and incorporate 3'-O-reversibly terminated nucleotides efficiently, allowing for longer DNA synthesis without the yield losses associated with conventional chemical methods.
2Productivity
If 'synthesize and stitch' technique is used to prepare nucleic acid strands, then DNA strands longer than 200 nucleotides can be produced, but the process becomes highly challenging and requires overlapping fragments to be stitched together
Solution Approach 1:
The patent extracts the stitching step from the synthesis process by using a modified TdT enzyme that can perform template-independent synthesis directly. Instead of synthesizing overlapping fragments and then stitching them together, the enzyme directly adds nucleotides to the 3' end of the target sequence, eliminating the need for fragment assembly and reducing process complexity.
Solution Approach 2:
The modified TdT enzyme serves multiple functions: it catalyzes nucleotide addition, incorporates 3'-O-reversibly terminated nucleotides, and operates at higher temperatures. This multi-functionality replaces the need for multiple separate processes (fragment synthesis, optimization, and stitching), simplifying the overall workflow for producing long DNA strands.
3Ease of operation
If conventional TdT is used for de novo single-stranded DNA synthesis, then uncontrolled dNTP addition occurs, but controlled extensions require complex termination technology
Solution Approach 1:
The patent changes the enzyme's parameters through amino acid modifications that enhance its catalytic efficiency and temperature stability. The modified TdT enzyme maintains controlled extension capability while operating at higher temperatures, eliminating the need for complex termination technology and simplifying the synthesis process.
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
These modified enzymes significantly improve the ability to synthesize longer DNA strands by increasing catalytic efficiency and temperature tolerance, overcoming limitations of existing methods and enabling more efficient nucleic acid synthesis.
Implementation Method 1
Modified terminal deoxynucleotidyl transferase (TdT) enzymes with enhanced catalytic activity and temperature stability, incorporating specific amino acid modifications such as E456G, R457S, and N473G, enable efficient incorporation of 3′-O-reversibly terminated nucleotides for de novo single-stranded DNA synthesis.
Implementation Method 2
The development of a controlled single-stranded DNA synthesis process through TdT would be invaluable to in situ DNA synthesis for gene assembly or hybridization microarrays
Data Source
AI summary
The invention relates to engineered terminal deoxynucleotidyl transferase (TdT) enzymes or the homologous amino acid sequence of Polμ, Polβ, Polλ, and Polθ of any species or the homologous amino acid sequence of X family polymerases of any species and uses thereof.