Mutant Pfu Polymerase for High-Density Fluorescent Labeling
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Solution Overview
Problem
Current DNA polymerases struggle to incorporate fluorescently labeled nucleotides at high densities, especially in PCR reactions, due to steric crowding and sequence bias, limiting their use in applications like microarray hybridization and single-molecule sequencing.
Innovation Solution
Engineering a mutant Pfu polymerase, such as E10, with an expanded substrate range through compartmentalized self-replication, allowing for the efficient incorporation of Cy5-dCTP and Cy3-dCTP at 100% substitution in both ELISA extension reactions and PCR, enhancing fluorescent labeling density and signal intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If naturally occurring or commercially available polymerase enzymes are used for direct incorporation of fluorescent labelled nucleotides, then the polymerase maintains high selectivity for correct nucleotide substrate, but the incorporation efficiency of fluorescent labelled nucleotides is low and exhibits significant sequence bias
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues in the polymerase enzyme (such as changing Arginine to Isoleucine at position 407, or Aspartic acid to Asparagine at position 399) to alter the enzyme's substrate binding properties. These parameter changes in the enzyme structure enable it to accommodate bulky fluorescent moieties while maintaining catalytic activity, thereby resolving the contradiction between nucleotide selectivity and fluorescent nucleotide incorporation efficiency
2Productivity
If dye-labelled nucleotide is spiked at low percentage into standard reaction mix to overcome polymerase discrimination, then the polymerase can incorporate the modified nucleotide, but the achieved fluorophore density is low
Solution Approach 1:
By changing the parameters of the polymerase enzyme through site-directed mutagenesis (specifically mutating residues in the nucleotide binding pocket), the patent enables the enzyme to accept high percentages (up to 100%) of fluorescently labelled nucleotides in the reaction mix. This resolves the contradiction by allowing both high modified nucleotide incorporation and high fluorophore density to be achieved simultaneously
3Quantity of substance
If indirect labelling technology is used to achieve higher fluorescent nucleic acid labelling densities, then complete substitution of every reactive nucleotide cannot be achieved
Solution Approach 1:
The patent extracts the limiting factor (polymerase substrate discrimination) by using a mutant polymerase with relaxed specificity. This extracted solution enables direct incorporation of fluorescent nucleotides at 100% substitution levels, surpassing the capabilities of indirect labelling methods and achieving both high fluorescent labelling density and complete substitution
4Reliability
If polymerase enzymes are used to incorporate fluorescent labelled nucleotides, then the enzymes discriminate against nucleotides bearing bulky side groups, but incorporating them at low level still shows sequence bias
Solution Approach 1:
The patent applies parameter changes by mutating amino acid residues (such as R407I, D399N, or E399D mutations) to expand the enzyme's substrate acceptance range. These parameter changes allow the polymerase to incorporate nucleotides with bulky fluorescent side groups without sequence bias, achieving both high incorporation accuracy and substrate flexibility
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 polymerase achieves a 7-fold higher fluorescent signal in microarray hybridization and a 4-fold increase with 10% substitution, demonstrating improved affinity and ability to incorporate detection agent labels into nucleic acids, thereby enhancing the sensitivity of PCR and other nucleic acid-based techniques.
Implementation Method 1
The engineered polymerase is capable of incorporating an enhanced occurrence of detection agent-labelled nucleotide analogue into nucleic acid synthesised by that engineered polymerase
Implementation Method 2
Fluorescence-based technologies have superseded radioisotopic detection as the preferred choice for labelling and detecting biomolecules
Data Source
AI summary
The present invention relates to an engineered polymerase with an expanded substrate range characterized in that the polymerase is capable of incorporating an enhanced occurrence of detection agent-labeled nucleotide analogue into nucleic acid synthesized by that engineered polymerase as compared with the wild type polymerase from which it is derived.