Engineered DNA Polymerase Nucleotide Discrimination
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Solution Overview
Problem
Current DNA sequencing technologies face challenges in effectively discriminating between cognate and non-cognate nucleotides during the sequencing process, particularly in the absence of cognate nucleotides, leading to reduced accuracy in identifying the next correct nucleotide for DNA replication.
Innovation Solution
Engineered DNA polymerases with specific amino acid substitutions, such as at positions K250, Q281, D355, and D532, are developed to enhance discrimination between cognate and non-cognate nucleotides by altering their affinity for primed template nucleic acids, allowing for improved identification of the next correct nucleotide through reduced binary complex formation and stabilized ternary complex formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If naturally occurring DNA polymerases are used, then DNA replication occurs, but discrimination between cognate and non-cognate nucleotides is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of DNA polymerase through site-directed mutagenesis. Specific residues (e.g., E290, Q281, D355, Q425, D532) are mutated to alter the enzyme's binding affinity characteristics, enabling reduced binary complex formation while maintaining or enhancing ternary complex stability, thereby improving nucleotide discrimination accuracy
Solution Approach 2:
The patent implements local quality by making targeted amino acid substitutions at specific positions within the polymerase active site and nucleotide binding regions. These localized changes (e.g., E290Q, Q281E, D355E) modify the chemical properties of specific residues to enhance discrimination capability without compromising overall enzymatic function
2Strength
If polymerase affinity for primed template is increased, then binding is enhanced, but binary complex formation increases reducing discrimination capability
Solution Approach 1:
The patent applies dynamics by creating polymerases with conditional binding characteristics. The engineered polymerases exhibit dynamic behavior where binding affinity is modulated by nucleotide presence: weak binary complex formation in the absence of cognate nucleotides versus stable ternary complex formation when cognate nucleotides are present, enabling discrimination through differential binding dynamics
Solution Approach 2:
The patent changes the binding parameter profile of the polymerase through amino acid mutations. The modifications alter the energy landscape of complex formation, reducing the stability constant for binary complexes while maintaining or enhancing ternary complex stability, thereby achieving discrimination through parameter optimization
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 DNA polymerases exhibit enhanced discrimination between cognate and non-cognate nucleotides, leading to improved accuracy in identifying the next correct nucleotide, thereby enhancing the sequencing process and reducing errors in DNA replication.
Implementation Method 1
the engineered DNA polymerase has a reduced affinity for the primed template nucleic acid in the absence of a cognate nucleotide, and exhibits a differential affinity for the primed template nucleic acid in the presence and absence of a cognate nucleotide
Data Source
AI summary
Provided are engineered DNA polymerases exhibiting modified functionality, and polynucleotides encoding same. Modified features include: (1) reduced catalytic activity in the presence of magnesium ions and/or (2) reduced affinity for primed template nucleic acid molecules in the absence of cognate nucleotide, and an ability to discriminate between cognate and non-cognate nucleotides under low salt conditions. Sequencing By Binding™ procedures employing the engineered polymerases have certain advantages. The engineered polymerases can have other uses as well.