Alpha-Synuclein Substrate Codon Optimization for SAA Diagnostics
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Solution Overview
Problem
Current monomeric αS substrates used in Seed Amplification Assay (SAA) for detecting misfolded αS protein in synucleinopathies face challenges such as self-aggregation and misfolding, leading to false positives and negatives due to cysteine misincorporation and insufficient homology with soluble misfolded αS protein, which complicates accurate diagnosis.
Innovation Solution
An expression vector optimized to avoid cysteine misincorporation at specific positions, producing a monomeric αS substrate with reduced self-aggregation, using codons that mitigate amino acid misincorporation, and a method involving acid precipitation and chromatography for purification to yield a recombinant αS substrate that effectively aggregates with soluble misfolded αS protein.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If monomeric αS substrate is produced using standard expression vectors in enterobacterial host cells, then production scale is sufficient for widespread testing, but cysteine misincorporation occurs leading to self-aggregation and false positives
Solution Approach 1:
The patent modifies the nucleic acid sequence parameters (codon selection) to change the amino acid incorporation outcome. Specifically, it uses codons that are not recognized by mischarged tRNAs in E. coli, thereby preventing cysteine misincorporation while maintaining efficient protein expression and avoiding self-aggregation.
2Difficulty of detecting and measuring
If monomeric αS substrate is used in Seed Amplification Assay, then detection of misfolded αS protein is enabled, but self-aggregation of the substrate causes false positives and reduces measurement precision
Solution Approach 1:
The patent changes the codon composition parameters of the αS substrate gene to eliminate cysteine misincorporation, thereby preventing aberrant self-aggregation. This maintains the substrate's ability to detect misfolded αS protein while eliminating false positive signals, thus improving measurement precision.
3Ease of manufacture
If standard nucleic acid sequences are used for αS protein expression in E. coli, then expression is achieved, but misincorporation of cysteine in place of tyrosine occurs at specific positions
Solution Approach 1:
The patent modifies the nucleic acid sequence parameters by selecting specific codons that are resistant to mischarging by E. coli tRNAs. This maintains protein expression capability while ensuring accurate amino acid incorporation, preventing cysteine substitution of tyrosine at positions 136 and other susceptible sites.
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 optimized monomeric αS substrate decreases self-aggregation, enhances detection accuracy, and maintains activity in the presence of soluble misfolded αS protein, improving diagnostic reliability by reducing false positives and negatives.
Implementation Method 1
a method involving acid precipitation and chromatography for purification
Implementation Method 2
a method involving acid precipitation and chromatography for purification
Implementation Method 3
maintains activity in the presence of soluble misfolded αS protein, improving diagnostic reliability
Data Source
AI summary
An expression vector is provided for production of human alpha-synuclein (αS) protein or a conservative variant thereof that exhibits a decreased tendency to self-aggregate in an αS seed amplification assay (SAA). The expression vector comprises a nucleic acid sequence coding for human αS protein or a conservative variant, the nucleic acid sequence comprising codons that have been optimized to produce human αS protein or a conservative variant when expressed by a host cell such as E. coli. The codons have been optimized to avoid amino acid misincorporation in the expressed protein. Methods for purification of the expressed protein are also provided.