Engineered Protein G Fab Binding Domains
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Solution Overview
Problem
Current immunoglobulin binding proteins (IBPs) like Protein-A and Protein-G have limitations due to their low affinity for the Fab domain of antibodies, which restricts their applications in purification and detection processes.
Innovation Solution
Engineered polypeptides with modified Fab constant regions and protein G Fab binding domains, specifically designed to enhance affinity for the Fab domain, are developed, including substitutions and deletions in amino acid sequences to improve binding capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Protein-G is used as an immunoglobulin binding protein, then it can bind to the Fc region of IgG, but its affinity for the Fab domain is too low (KD ~low μM)
Solution Approach 1:
The patent modifies specific local regions of the Protein-G structure, particularly the C2 domain, by introducing point mutations and deletions at specific amino acid positions (e.g., positions 78, 139, 142) to enhance Fab binding affinity while preserving overall protein structure and function
Solution Approach 2:
The patent systematically alters biochemical parameters of Protein-G including amino acid sequence composition, molecular weight (through deletions), and structural conformation to transform it from a Fc-binding protein to a high-affinity Fab-binding protein with KD in the nanomolar range
2Productivity
If Protein-A or Protein-G are used for Fab domain purification, then purification can be performed, but the low affinity limits efficiency and application scope
Solution Approach 1:
The patent optimizes multiple parameters simultaneously including binding affinity (KD), specificity, and purification capacity by engineering modified Protein-G variants that exhibit enhanced Fab binding characteristics for improved purification productivity
Solution Approach 2:
The patent creates composite functional properties by combining elements of Protein-G structure with engineered modifications to produce a hybrid molecule that retains stability and solubility while gaining enhanced Fab binding capability
Data Source
AI summary
The engineered polypeptide comprising modified Fab constant regions and/or protein G Fab binding domains provide advanced affinity reagents that can be used in cell biology applications as well as for therapeutic applications. Accordingly, aspects of the disclosure relate to a polypeptide comprising a constant region of an antibody light chain, wherein the constant region comprises a substitution/deletion of amino acids corresponding to positions 16-20 of SEQ ID NO:1 of the constant region with the amino acids LRT.