Modified SpA Domain Affinity Ligand for IgG Purification
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Solution Overview
Problem
Affinity chromatography carriers using Staphylococcus aureus protein A (SpA) domains for immunoglobulin purification face challenges due to low immunoglobulin-binding capacity and alkali resistance issues, leading to high costs and reduced efficiency under alkaline cleaning conditions.
Innovation Solution
A modified immunoglobulin-binding protein with inserted amino acid residues between positions 3 and 4 of the B, Z, or C domains of SpA is used, enhancing binding capacity and alkali resistance, allowing for efficient immunoglobulin purification with reduced carrier usage and prolonged carrier lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural-type SpA or its domains are used as affinity chromatography ligands, then immunoglobulin purification is achieved, but the immunoglobulin-binding capacity remains low due to steric hindrance from crooked domain arrangement
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence at specific positions (positions 3 and 4) in the SpA domains. By changing the structural parameters of the domain arrangement through amino acid substitution, the crooked configuration is corrected to a more linear arrangement, thereby reducing steric hindrance and improving immunoglobulin-binding capacity without changing the overall domain structure
Solution Approach 2:
The patent creates modified copies of the SpA domains (B domain, C domain, or Z domain) with specific amino acid changes at positions 3 and 4. These copied and modified domains are then linked together to form the affinity ligand, ensuring consistent linear arrangement across all domain units in the multi-domain construct
2Productivity
If SpA-based affinity chromatography carriers are used for immunoglobulin purification, then purification is achieved, but production costs are very high
Solution Approach 1:
By modifying the amino acid parameters at positions 3 and 4 in the SpA domains, the patent enhances the binding capacity per unit of carrier. This parameter change allows fewer carrier units to achieve the same purification throughput, thereby reducing the quantity of expensive SpA-based carrier material needed while maintaining high purification efficiency
3Ease of operation
If alkaline cleaning-in-place (CIP) is used to clean affinity chromatography carriers, then contaminants are removed, but the ligands lose binding capacity due to deamidation of Asn and Gln residues
Solution Approach 1:
The patent extracts or removes the problematic Asn and Gln residues at positions 3 and 4 from the SpA domain sequence. By taking out these alkali-sensitive amino acids, the ligand becomes resistant to deamidation during alkaline CIP cleaning, thereby maintaining binding capacity stability across multiple cleaning cycles while still allowing effective contaminant removal
Solution Approach 2:
The patent converts the potential harm of alkaline cleaning (which would cause deamidation) into a benefit by pre-modifying the amino acid sequence to be alkali-resistant. The alkaline CIP process that would normally damage the ligand now serves to cleanly clean the carrier without affecting ligand functionality, extending carrier lifespan and maintaining reliability
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 immunoglobulin-binding protein maintains high immunoglobulin-binding capacity and alkali resistance, enabling cost-effective and efficient immunoglobulin purification even after repeated alkaline cleaning, reducing the need for large carrier quantities and extending carrier usage.
Implementation Method 1
Affinity chromatography is chromatography that uses a column packed with a ligand-immobilized carrier, in which a substance (ligand) that specifically binds to a substance intended to be separated or purified is immobilized on an insoluble carrier
Data Source
AI summary
Provided is an affinity chromatography carrier that maintains high immunoglobulin-binding capacity and high alkali resistance. An immunoglobulin-binding protein including at least one modified immunoglobulin-binding domain, the modified immunoglobulin-binding domain being a polypeptide consisting of an amino acid sequence of an immunoglobulin-binding domain selected from the group consisting of the B domain, Z domain, C domain, and variants thereof of Staphylococcus aureus protein A, in which at least one amino acid residue is inserted between positions corresponding to the 3-position and position 4 of the amino acid sequence of the B domain, Z domain or C domain.