Archaeal DNA Polymerase Uracil-Binding Pocket Mutation
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Solution Overview
Problem
Native archaeal DNA polymerases are inhibited by deoxyuracil, which is introduced during PCR due to thermal deamination of dCTP to dUTP, making them unsuitable for PCR applications, especially those requiring the prevention of carry-over contamination.
Innovation Solution
A variant archaeal DNA polymerase with a modified amino acid sequence in the uracil-binding pocket, reducing its affinity for uracil, allowing it to function effectively in the presence of dUTP without stalling polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If native archaeal DNA polymerase is used, then thermal stability and proofreading activity are achieved, but the polymerase is inhibited by deoxyuracil causing amplification to stall
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues (such as Y7A, Y37A, V93Q, P115Δ) in the uracil-binding pocket of the archaeal DNA polymerase. These mutations alter the binding parameters of the polymerase to uracil, reducing its affinity for deoxyuracil while maintaining thermal stability and proofreading activity. This allows the polymerase to function effectively in PCR reactions containing dUTP.
2Productivity
If Taq DNA polymerase is used, then amplification efficiency is high, but the enzyme lacks proofreading activity resulting in base incorporation errors
Solution Approach 1:
The patent achieves universality by creating a modified archaeal DNA polymerase that combines multiple functions: thermal stability (allowing high-temperature PCR), proofreading activity (removing mismatched bases), and resistance to deoxyuracil inhibition (enabling use with dUTP). This multi-functional enzyme resolves the contradiction between amplification efficiency and proofreading capability found in Taq polymerase.
3Object-affected harmful factors
If dUTP is used in PCR to prevent carry-over contamination, then contamination prevention is improved, but native archaeal polymerases are inhibited causing amplification failure
Solution Approach 1:
The patent converts the harmful effect of deoxyuracil (which normally inhibits archaeal polymerases) into a beneficial feature. By mutating the uracil-binding pocket, the polymerase becomes resistant to deoxyuracil inhibition, allowing it to function in dUTP-containing reactions. This enables the use of dUTP for carry-over contamination prevention while maintaining successful amplification.
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 variant polymerase maintains thermal stability and proofreading ability while avoiding inhibition by dUTP, enabling successful PCR amplification even in conditions where dUTP is used, thus addressing the issue of carry-over contamination.
Implementation Method 1
the polymerase builds a new strand by joining free bases to the primers thereby producing a new strand
Implementation Method 2
this enzyme does not possess a 3′-5′ exonuclease III function, commonly referred to as 'proofreading activity'. This function removes bases that are mismatched
Implementation Method 3
the modified sequence being in the amino-terminal amino acids that comprise a uracil-binding pocket in the wild-type polymerase whereby the variant polymerase has reduced affinity for uracil
Data Source
AI summary
The present invention relates to a variant archaeal DNA polymerase having a modified amino acid sequence of a wild-type amino acid sequence, the modified sequence being in the amino-terminal amino acids that comprise a uracil-binding pocket in the wild-type polymerase whereby the variant polymerase has reduced affinity for uracil than the wild-type polymerase. Such variant polymerases may be usefully employed in biological assay systems such as the polymerase chain reaction.