Split Glutamine Synthetase Vectors for Balanced Antibody Expression
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Solution Overview
Problem
Existing expression systems struggle to produce heteromeric protein complexes, such as antibodies, by ensuring equal expression of heavy and light chains, leading to inefficient production due to imbalanced expression levels.
Innovation Solution
The use of glutamine synthetase fragments, split at specific amino acid positions, to form a functional multimeric protein that provides a selectable marker, ensuring equal expression of heteromeric complexes by linking each chain's expression to the requirement for functional glutamine synthetase in a selective medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional expression systems are used to produce heteromeric protein complexes, then production can proceed with standard methods, but expression levels of different polypeptides become imbalanced leading to inefficient production
Solution Approach 1:
The glutamine synthetase gene is divided into two separate fragments (GS1 and GS2), each fused to different polypeptide chains (heavy chain and light chain). This segmentation ensures that both chains must be expressed at appropriate levels to form the functional enzyme, thereby resolving the imbalance problem in heteromeric complex production.
Solution Approach 2:
Instead of directly controlling the expression of each polypeptide chain separately, the invention inverts the approach by making the expression of a functional glutamine synthetase enzyme dependent on the balanced expression of both chains. The selection pressure for enzyme functionality automatically enforces balanced polypeptide expression.
2Measurement precision
If selection methods are used to identify cells expressing high levels of proteins, then high expression cells can be selected, but the time required for selection is extended
Solution Approach 1:
The expression system incorporates a self-selecting mechanism where cells that successfully express both polypeptide chains at appropriate levels automatically gain the ability to produce functional glutamine synthetase. This functional enzyme provides inherent selection advantage in glutamine-free media, eliminating the need for time-consuming external selection procedures.
3Quantity of substance
If one polypeptide chain is expressed at high levels, then that chain is readily available, but the corresponding partner chain is expressed at insufficient levels preventing proper association
Solution Approach 1:
The invention merges the expression control of both polypeptide chains through their respective fusions to glutamine synthetase fragments. The functional enzyme acts as a unified system where both chains are required for activity, ensuring that sufficient quantities of both chains are produced and properly associated to form the heteromeric complex.
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 robust and high-level expression of heteromeric proteins, reducing the time required for selecting cells expressing high levels of proteins and ensuring proper association of polypeptides.
Implementation Method 1
there is provided a first fragment of glutamine synthetase and a second fragment of glutamine synthetase. The first and second fragments of glutamine synthetase can interact and/or associate to form a monomer and then a functional multimeric glutamine synthetase protein.
Implementation Method 2
the first and second fragments of glutamine synthetase associate to provide a selectable activity
Data Source
AI summary
Inventions disclosed herein relates to vectors and expression systems for producing heteromeric recombinant proteins such as monoclonal antibodies. Vectors and expression systems disclosed herein are based on the finding that the selectable marker glutamine synthetase can be divided into two fragments at selected amino acid positions of the glutamine synthetase polypeptide, and the two fragments can internet and/or associate to form a monomer and then a functional multimeric glutamine synthetase protein.