Heat-Resistant Reverse Transcriptase Mutant for cDNA Synthesis
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Solution Overview
Problem
Current reverse transcriptases, such as those from Moloney murine leukemia virus and avian myeloblastosis virus, have poor heat resistance, which limits their effectiveness in synthesizing cDNA from mRNA with secondary structures, as increasing temperature to prevent secondary structure formation inactivates these enzymes.
Innovation Solution
Development of reverse transcriptase mutants by replacing threonine at position 55 with amino acids having non-polar aliphatic, polar acidic, polar basic, or polar hydroxy aliphatic side chains, combined with additional mutations like A54P, T287K, and D524A, to enhance heat resistance without affecting RNA binding and cDNA elongation activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the temperature of reverse transcription reaction is raised to prevent secondary structure formation of RNA, then the RNA secondary structure is suppressed, but the reverse transcriptase is inactivated due to poor heat resistance
Solution Approach 1:
The invention changes the amino acid parameters of the reverse transcriptase enzyme through site-directed mutagenesis. Specifically, it replaces amino acids at positions 53-56 (particularly position 55) with variants that have different physical and chemical properties to enhance thermal stability while preserving catalytic function, allowing the enzyme to remain active at higher temperatures (50-65°C) needed to suppress RNA secondary structures
Solution Approach 2:
The invention creates a composite enzyme structure by combining multiple amino acid substitutions in the loop region (positions 53-56) with the rest of the wild-type reverse transcriptase structure. This composite approach integrates stabilizing mutations into the existing enzyme framework, achieving both heat resistance and maintained catalytic activity
2Temperature
If amino acid mutations are introduced to increase heat resistance, then the heat resistance is improved, but the loop structure stability may be affected
Solution Approach 1:
The invention applies local quality changes by introducing amino acid mutations specifically in the loop region (positions 53-56) of the reverse transcriptase molecule, while leaving the rest of the enzyme structure unchanged. This localized approach allows optimization of thermal stability in the loop region without disrupting the overall enzyme architecture and catalytic function
Solution Approach 2:
The invention changes the physical and chemical parameters of amino acids at positions 53-56 to enhance loop stability at elevated temperatures. By selecting amino acids with appropriate properties (e.g., hydrophobicity, charge, size), the loop structure is stabilized to maintain enzyme integrity and activity at higher temperatures
Data Source
AI summary
Provided are: a reverse transcriptase mutant including an amino acid mutation at a position corresponding to position 55 of the amino acid sequence of wild-type reverse transcriptase derived from the Moloney murine leukemia virus, wherein the reverse transcriptase mutant is characterized in that the amino acid mutation is a substitution from threonine to another amino acid, and the other amino acid is selected from the group consisting of amino acids having a nonpolar aliphatic side chain and amino acids having a polar acidic functional group side chain; a nucleic acid that encodes the mutant; a method for producing the mutant and the nucleic acid that encodes the mutant; a method for synthesizing cDNA in which the mutant is used; and a composition and kit including the mutant.