Sortase Conjugation Loop for Site-Specific Antibody Labeling
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Solution Overview
Problem
Current methods for site-specific modification of proteins, particularly antibodies, face challenges such as decreased antigen-binding activity, low yields, and mixture formation due to non-specific labeling strategies, which are not economically viable for industrial-scale applications.
Innovation Solution
Introduction of a sortase conjugation loop between the C-terminal most cysteine of the middle hinge region and the CH2-domain of immunoglobulin heavy chains, enabling sortase-mediated cleavage and ligation for site-specific conjugation of antibody fragments like F(ab')2, using a sortase nucleophile with a pentaglycine motif for efficient and controlled labeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lysine-labeling strategy is used to label antibodies, then labeling can be performed using abundant and easily modified residues, but antigen-binding activity significantly decreases and yields of desired 1:1 product are low
Solution Approach 1:
The antibody heavy chain is segmented to include a separate sortase recognition motif (LPXTG sequence) distinct from the antigen-binding regions. This allows site-specific modification at the hinge region without affecting antigen-binding sites, resolving the contradiction between ease of labeling and preservation of antigen-binding activity
Solution Approach 2:
Sortase enzyme is introduced as an intermediary to mediate the conjugation reaction. The enzyme specifically recognizes the LPXTG motif and catalyzes the attachment of labels or other molecules with high precision, enabling easy manufacturing while maintaining antibody functionality through controlled, site-specific modification
2Ease of manufacture
If lysine-labeling strategy is used, then labeling can be performed with available coupling chemistry, but mixtures of labels attached via different lysines are formed and yields are low
Solution Approach 1:
The antibody is engineered with a unique local quality - a sortase recognition motif (LPXTG sequence) at a specific location in the hinge region. This creates a single, defined site for labeling that differs from all other regions of the antibody, ensuring that labels are attached uniformly at one specific location rather than distributed across multiple lysine residues, thereby achieving high manufacturing precision while maintaining ease of manufacture through standard enzymatic coupling chemistry
3Ease of manufacture
If traditional labeling methods are used, then labeling can be performed with simple chemistry, but the process is not economically viable for industrial-scale applications
Solution Approach 1:
The antibody molecule itself provides the sortase recognition motif that enables specific labeling. The engineered LPXTG sequence acts as a self-service feature that guides the sortase enzyme to the correct location, eliminating the need for complex protection-deprotection strategies or multiple purification steps. This self-directing capability simplifies the overall process and improves productivity for industrial-scale production by reducing manufacturing complexity while maintaining labeling precision
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
This approach allows for high-yield, site-specific conjugation of antibody fragments with preserved antigen-binding activity, overcoming the limitations of traditional labeling methods by providing a controlled and efficient method for industrial-scale production.
Implementation Method 1
The sortase enzyme cleaves between the residues threonine (T) and X2 (G or A). The reaction proceeds through a thioester acyl-enzyme intermediate
Implementation Method 2
The ligation motif on the sortase nucleophile (also referred to as sortase substrate), i.e. the polypeptide part of the peptidoglycan that becomes attached to the substrate on the bacterial cell wall, naturally is a pentaglycine motif. The reaction proceeds through a thioester acyl-enzyme intermediate, which is resolved by the attack of an amine nucleophile from the oligoglycine, thereby covalently linking the peptidoglycan to a protein substrate
Data Source
AI summary
The disclosure describes a recombinant immunoglobulin heavy chain comprising a sortase conjugation loop, methods for conjugating and/or labeling such recombinant immunoglobulin heavy chains by use of the enzyme sortase and to the conjugates/labeled products obtained via the method.