Modified Protein A Ligand for Stable Immunoglobulin Purification
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Solution Overview
Problem
Affinity chromatography carriers for immunoglobulin purification face challenges in achieving high immunoglobulin-binding capacity, chemical stability, and cost-effectiveness, with existing methods either releasing ligands under acidic conditions or failing to control orientation for optimal binding.
Innovation Solution
A modified immunoglobulin-binding protein with enhanced orientation and chemical stability is developed by increasing lysine residues on the protein surface and eliminating the aspartic acid-proline sequence, allowing for controlled immobilization and improved binding capacity under various pH conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protein A is immobilized on an affinity carrier via thioester bond at one cysteine residue, then chemical stability is improved, but immunoglobulin-binding capacity is reduced due to limited orientation control
Solution Approach 1:
The patent changes the chemical parameters of the protein by introducing multiple cysteine residues at specific positions (positions 3, 7, 12, 17, 22, 27, 32, 37, 42, 47, 52, 57) to enable diverse immobilization orientations. This parameter change allows the protein to maintain chemical stability through covalent bonding while simultaneously improving immunoglobulin-binding capacity through enhanced orientation control on the affinity carrier surface.
Solution Approach 2:
The patent creates a composite structure by combining the protein A backbone with multiple strategically placed cysteine residues, forming a modified protein A variant that integrates both stability and binding capacity functions. This composite approach allows simultaneous achievement of chemical stability through thioester bond formation and high binding capacity through multiple potential immobilization sites.
2Reliability
If protein A is immobilized at multiple points to prevent ligand release, then chemical stability is improved, but orientation control is lost reducing binding efficiency
Solution Approach 1:
The patent modifies the protein structure by introducing multiple cysteine residues at specific positions, changing the immobilization parameters from single-point to multi-point attachment. This allows the protein to be firmly anchored (improving stability) while maintaining flexible orientation control through selective activation of specific cysteine residues during the immobilization process.
3Reliability
If natural protein A is used as affinity ligand, then immunoglobulin-binding activity is maintained, but cost of production increases
Solution Approach 1:
The patent applies local quality modification by introducing cysteine residues only at specific positions (3, 7, 12, 17, 22, 27, 32, 37, 42, 47, 52, 57) rather than throughout the entire protein sequence. This localized modification maintains the natural protein's immunoglobulin-binding activity while enabling improved immobilization properties, and can be produced cost-effectively through targeted site-directed mutagenesis in recombinant expression systems.
4Productivity
If affinity carrier is designed for high binding capacity, then immunoglobulin purification efficiency is improved, but ligand leakage under acidic conditions occurs
Solution Approach 1:
The patent takes preliminary action by pre-installing multiple cysteine residues at strategic positions within the protein sequence before immobilization. This preliminary structural preparation ensures that when the protein is subsequently immobilized on the affinity carrier, it forms stable covalent bonds that prevent ligand leakage under acidic elution conditions, while simultaneously maintaining high binding capacity through optimal orientation.
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 protein achieves high immunoglobulin-binding capability, chemical stability, and reduced ligand leakage, enabling efficient and cost-effective immunoglobulin purification.
Implementation Method 1
a modified protein obtained by modifying an immunoglobulin-binding protein so as to have improved properties as an affinity ligand for affinity chromatography
Data Source
AI summary
Provided is affinity chromatography carrier for an immunoglobulin that simultaneously has high immunoglobulin-binding capability and chemical stability and that can be produced at low cost. An immunoglobulin-binding protein in which an amino acid substitution for not only maximizing the number of lysine residues on the protein surface of helix 3 and its periphery but also minimizing the number of lysine residues present on the protein surfaces of helix 1 and helix 2 as immunoglobulin-binding regions and/or an amino acid substitution for eliminating an aspartic acid-proline sequence have (has) been carried out, or a multimer thereof, is used as an affinity ligand for an affinity chromatography carrier.