Engineered Protein A Ligand for Controlled Immobilization
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Solution Overview
Problem
Current affinity separation matrices for antibody purification, such as those using Protein A, face challenges in achieving optimal binding capacity and efficiency, particularly in maintaining the affinity of engineered proteins with substitutions for all Lys residues and additional terminal Lys residues.
Innovation Solution
Development of recombinant Protein A variants with specific amino acid substitutions and terminal Lys additions, allowing efficient immobilization through the ε-amino group of Lys, which maintains or improves binding capacity and affinity to target molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Protein A is immobilized on a water-insoluble carrier through multiple Lys residues, then the immobilization capacity is improved, but the orientation control becomes difficult and binding efficiency decreases
Solution Approach 1:
The invention extracts the Lys residues from the antibody-binding surface of Protein A, removing them to prevent random immobilization through multiple sites. This leaves only the terminal Lys for controlled immobilization, resolving the contradiction between immobilization capacity and orientation control
Solution Approach 2:
The invention creates local quality differentiation by specifically modifying only the terminal region of Protein A with a single Lys residue, while maintaining the original structure and function of the antibody-binding domains. This localized modification enables controlled immobilization without affecting binding efficiency
2Quantity of substance
If Protein A variants with substitutions for all Lys residues are used, then the binding capacity is improved, but the stability under alkali conditions deteriorates
Solution Approach 1:
The invention changes the chemical parameter of the terminal residue from Lys to a more alkali-stable amino acid (such as Arg or Lbu), which maintains the positive charge necessary for immobilization while providing resistance to alkali degradation. This parameter change resolves the contradiction between binding capacity and alkali 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 engineered Protein A variants demonstrate high binding capacity and efficiency even with reduced immobilized ligand amounts, offering cost-effective performance and improved stability under alkali conditions.
Implementation Method 1
The ligand is immobilized on the carrier through the Lys residue (through its side chain ε-amino group) by reductive amination or the like
Implementation Method 2
Protein A is a cell wall protein produced by the gram-positive bacterium Staphylococcus aureus, and contains a signal sequence S, five immunoglobulin-binding domains
Data Source
Figure 1~2
Figure 3(1)~3
AI summary
An object of the present invention is to provide a technique to create novel engineered protein ligands that, when immobilized through a lysine residue (its side chain ε-amino group) which allows for efficient immobilization to a carrier, show the optimum binding capacity and binding efficiency to a target molecule. The present invention provides an engineered protein having a sequence obtained by replacing all the lysine residues in Protein A, which is the most typical protein ligand, with other amino acids, and adding lysine at a terminal; and an affinity separation matrix in which such an engineered protein is immobilized on a water-insoluble carrier by reductive amination or the like. This affinity separation matrix is characterized by its high binding capacity to a target molecule even when the immobilized amount of the ligand is small.