Mutant Beta Glucuronidase Enhances Immunoassay Sensitivity
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Solution Overview
Problem
Current homogeneous immunoassays for antigen detection, while sensitive, require improvements in sensitivity for clinical diagnostics, particularly in the field of medicine.
Innovation Solution
A mutant β glucuronidase with specific amino acid substitutions, such as methionine at position 516 substituted with lysine and tyrosine at position 517 substituted with tryptophan, is used to create a fusion protein that enhances enzyme activity in the presence of an antigen and reduces background activity, enabling more sensitive antigen detection through tetramer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a GUS mutant with M516K and Y517E substitutions is used for antigen detection, then detection sensitivity is improved, but further sensitivity enhancement is needed for clinical diagnostics
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of GUS mutant (changing Y517E to Y517W substitution) to alter the enzyme's tetramer formation characteristics. This parameter change in the protein structure results in enhanced signal value and reduced background value, thereby improving detection sensitivity to meet clinical diagnostic requirements
Solution Approach 2:
The patent creates a new GUS mutant variant (M516K/Y517W) that copies the successful M516K substitution from the previous mutant but replaces the Y517E substitution with Y517W to achieve superior performance. This copying and modification approach allows optimization of the detection system while maintaining the beneficial properties of the original mutant
2Measurement precision
If GUS forms tetramer in presence of antigen, then signal value increases, but background value also needs to be minimized for high sensitivity
Solution Approach 1:
The patent applies local quality by making specific localized changes to the GUS protein structure at positions 516 and 517. The M516K and Y517W substitutions locally modify the protein's interaction properties, enabling selective enhancement of tetramer formation (signal) while suppressing non-specific aggregation (background), thus improving the signal-to-background ratio
Solution Approach 2:
The patent inverts the approach by preventing tetramer formation under normal conditions (keeping GUS as dimer) and only allowing tetramer formation when antigen is present. The M516K/Y517W mutations are designed to disrupt spontaneous tetramerization while preserving antigen-induced tetramer formation, effectively inverting the normal aggregation behavior to achieve low background and high signal
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 mutant β glucuronidase fusion protein significantly increases signal value in the presence of an antigen and decreases background value, providing higher sensitivity and stability for antigen detection, addressing the need for improved sensitivity in clinical diagnostics.
Implementation Method 1
the interaction between the VH domain and the VL domain is enhanced, and this interaction allows a dimer of the mutant of GUS linked to the VH domain and that linked to the VL domain to bind together to form a tetramer, which in turn exhibits activity
Implementation Method 2
The measurement method utilizes such a characteristic of GUS, and uses two fusion proteins... measuring the activity of GUS
Data Source
AI summary
Provided as a mutant of β glucuronidase suitable for homogeneous immunoassays is a β glucuronidase mutant, wherein, in the amino acid sequence of Escherichia coli β glucuronidase, methionine at position 516 is substituted with lysine, and tyrosine at position 517 is unsubstituted or substituted with a non-tyrosine aromatic amino acid.