Factor B Cysteine Variant for Heat-Stable Endotoxin Detection
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Solution Overview
Problem
Existing horseshoe crab factor B variants do not exhibit superior protease activity and thermal stability compared to the native factor B, limiting their effectiveness in detecting microorganism-derived substances and measuring contamination.
Innovation Solution
Amino acid residue at position 193 in the factor B sequence is substituted with cysteine to create a variant with enhanced protease activity and thermal stability, along with nucleic acids encoding these variants and methods for their production and use in endotoxin measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If native horseshoe crab factor B is used, then the Limulus test can detect endotoxins, but the protease activity is insufficient and thermal stability is poor
Solution Approach 1:
The patent applies parameter changes by substituting specific amino acid residues (Ser193, Thr194, Ser195) in the factor B sequence with alternative residues (Ala, Val, Ile, Leu, Met, Phe, Trp, Tyr, Cys, Gly, Pro). This amino acid substitution strategy modifies the molecular parameters of factor B to enhance its protease activity while maintaining endotoxin detection capability, directly resolving the contradiction between sufficient protease activity and reliable endotoxin detection.
2Temperature
If native horseshoe crab factor B is used, then the test can proceed at physiological temperatures, but thermal stability is poor leading to loss of function at elevated temperatures
Solution Approach 1:
The patent uses parameter changes by introducing amino acid substitutions at positions 193-195 to enhance the thermal stability of factor B. These substitutions modify the molecular structure to resist thermal denaturation, allowing the factor B variant to maintain protease activity and endotoxin detection functionality at elevated temperatures where native factor B would lose function.
3Measurement precision
If factor B variants with higher protease activity are developed, then detection sensitivity improves, but the structural modifications may compromise thermal stability
Solution Approach 1:
The patent simultaneously optimizes multiple parameters by selecting specific amino acid substitutions that enhance both protease activity and thermal stability. The substitutions at positions 193-195 are chosen to improve catalytic efficiency for enhanced detection sensitivity while the resulting structural changes also fortify thermal resistance, thereby resolving the contradiction between detection sensitivity and thermal stability.
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 modified factor B variant demonstrates two to ten times higher protease activity and maintains functionality after heat exposure, improving the sensitivity and reliability of endotoxin detection.
Implementation Method 1
a horseshoe crab factor B variant having protease activity superior to that of the factor B itself
Implementation Method 2
a horseshoe crab factor B variant having thermal stability that is superior to that of the factor B itself
Data Source
AI summary
Provided is a technology related to a horseshoe crab factor B variant, and also provided is means for performing endotoxin measurement with high sensitivity. A polypeptide having an amino acid sequence in which the amino acid residue at the 193-position in an amino acid sequence of a polypeptide of horseshoe crab factor B is substituted with a cysteine (Cys) residue, is produced. Endotoxin measurement can be carried out with high sensitivity by combining this polypeptide with horseshoe crab factor C, as a Limulus reagent.