TAPE Method for Soluble VH VL Antibodies
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Solution Overview
Problem
Current methods for screening human immunoglobulin variable domain antibodies (VH or VL) face challenges in achieving high solubility and thermostability, which are essential for their stability and effectiveness as therapeutic proteins, particularly due to limitations in protein folding and aggregation issues within E. coli expression systems.
Innovation Solution
The Tat-associated protein engineering (TAPE) method involves fusing target proteins with a Tat signal sequence and TEM-1 beta-lactamase to the pET-TAPE vector, allowing expression in E. coli, where only properly folded proteins with high solubility can survive in a liquid medium with antibiotics, thereby selecting for proteins with enhanced solubility and thermostability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If human immunoglobulin variable domain antibodies are expressed in E. coli using conventional methods, then production is achieved, but solubility and thermostability are poor due to protein folding issues and aggregation
Solution Approach 1:
The patent introduces a Tat signal sequence as an intermediary element that mediates protein translocation from the cytoplasm to the periplasm. This intermediary mechanism allows properly folded proteins to reach the periplasm where they can be detected, while preventing aggregation in the cytoplasm. The Tat signal sequence acts as a selector that only permits correctly folded proteins to pass through, thereby enriching for soluble and thermostable variants.
Solution Approach 2:
The patent performs preliminary protein folding in the E. coli cytoplasm before translocation. By requiring proteins to fold correctly in the cytoplasm prior to crossing the membrane via the Tat pathway, the system pre-selects for properly structured proteins. This preliminary folding step ensures that only correctly folded, soluble proteins are translocated to the periplasm, where they can be further selected for thermostability.
2Reliability
If screening methods are developed to improve solubility and thermostability, then protein stability is enhanced, but screening complexity and time increase
Solution Approach 1:
The patent employs a self-service selection mechanism where the Tat signal sequence and antibiotic resistance system automatically filter for soluble and thermostable proteins without requiring manual intervention. Proteins that fold correctly and confer antibiotic resistance automatically survive and proliferate, while non-functional variants are eliminated. This self-selecting system dramatically reduces screening time compared to conventional methods that require manual assessment of each variant.
Solution Approach 2:
The patent implements a feedback loop where protein folding status and antibiotic resistance are continuously monitored during the screening process. The Tat signal sequence provides real-time feedback on protein folding quality, while antibiotic survival provides feedback on functional activity. This dual feedback mechanism enables rapid identification of improved variants, reducing the time required to screen large libraries while maintaining high selection accuracy.
3Reliability
If conventional screening methods are used, then existing antibodies can be tested, but they lack the solubility and thermostability required for effective therapeutic use
Solution Approach 1:
The patent fundamentally changes the screening parameters by shifting from conventional expression systems to a Tat pathway-based system with periplasmic targeting. This parameter change involves modifying the subcellular localization, folding environment, and selection mechanism. By changing these parameters, the system simultaneously improves solubility and thermostability while maintaining high screening efficiency through the antibiotic resistance selection system.
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 method effectively screens for VH or VL domain antibodies with improved solubility and thermostability, maintaining these properties regardless of CDR sequences, enabling their use as stable scaffolds for antigen binding and therapeutic applications.
Implementation Method 1
by fusing the target protein and an antibiotic-resistant protein to a Tat signal sequence and expressing this within E. coli
Implementation Method 2
fusing the target protein and an antibiotic-resistant protein to a Tat signal sequence and expressing this within E. coli
Data Source
Figure 1
Figure 2(a)~2(d)
Figure 3a
AI summary
There are provided a method named Tat-associated protein engineering (TAPE), of screening a target protein having higher solubility and excellent thermostability, in particular, an immunoglobulin variable domain (VH or VL) derived from human germ cells, by preparing a gene construct where the target protein and an antibiotic -resistant protein are linked to a Tat signal sequence, and then expressing this within E. coli, and human or engineered VH and VL domain antibodies and human or engineered VH and VL domain antibody scaffolds having solubility and excellent thermostability, which are screened by the TAPE method. There are also provided a library including random CDR sequences in the human or engineered VH or VL domain antibody scaffold screened by the TAPE method, and a preparing method thereof. There are also provided a VH or VL domain antibody having binding ability to the target protein screened by using the library, and a pharmaceutical composition including the domain antibody.