Recombinant Rubella E1 Antigen Segmentation for Solubility
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Solution Overview
Problem
Current methods for producing Rubella E1 antigens for diagnostic purposes face challenges such as aggregation, incorrect disulfide bonding, and low solubility, particularly in prokaryotic hosts, which limits their effectiveness in immunoassays due to their unglycosylated and cysteine-rich nature.
Innovation Solution
Development of recombinant Rubella E1 antigens lacking the C-terminal transmembrane region and anchor segment, with specific disulfide bridge combinations (e.g., Cys 225-Cys 235 to Cys 349-Cys 352) stabilized by oxidative refolding, expressed as chaperone fusion proteins in E. coli, ensuring high solubility and immunoreactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Rubella E1 antigens are produced in prokaryotic hosts, then production efficiency is improved, but solubility and correct disulfide bonding deteriorate due to aggregation
Solution Approach 1:
The E1 protein is divided into two separate polypeptide chains: chain A containing residues 1-242 with disulfide bridges C1-C2, C3-C15, C6-C7, C9-C10, C11-C12, and C13-C14; and chain B containing residues 243-452 with disulfide bridges C17-C18, C19-C20, and C21-C22. This segmentation reduces aggregation propensity while maintaining immunoreactivity, allowing successful expression in E. coli with correct disulfide bonding.
Solution Approach 2:
The invention uses a fusion partner (such as GST or MBP) as an intermediary during expression in E. coli, which facilitates correct folding and disulfide bond formation. The fusion partner acts as a molecular chaperone that prevents aggregation and promotes proper structural organization before the final antigen is obtained.
2Reliability
If full-length E1 protein is produced, then complete epitope representation is improved, but solubility deteriorates due to the transmembrane region and cysteine-rich nature
Solution Approach 1:
The transmembrane anchoring region (residues 453-481) is removed from the E1 protein sequence. This extraction eliminates the hydrophobic membrane-spanning segment that causes aggregation and insolubility in aqueous environments, while preserving the ectodomain epitopes required for antibody detection.
Solution Approach 2:
Different regions of the E1 protein are treated differently: the ectodomain regions containing epitopes are preserved with correct disulfide bonding, while the transmembrane region is removed. This local differentiation maintains immunoreactivity while improving overall solubility.
3Stability of the object's composition
If cysteine residues are retained for disulfide bonding, then structural stability is improved, but aggregation increases due to incorrect disulfide formation
Solution Approach 1:
By dividing E1 into chains A and B with specifically assigned disulfide bridges, the invention reduces the complexity of disulfide bond formation. Each chain has a defined number of cysteines that form predictable disulfide bonds, minimizing mispairing and aggregation while maintaining structural stability.
Solution Approach 2:
The invention changes the disulfide bonding parameters by defining specific pairings in the segmented structure. This controlled disulfide formation pattern, combined with optimization of oxidation conditions during purification, ensures correct structural stability without aggregation.
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 resulting antigens are highly soluble, stable, and immunoreactive, effectively detecting anti-Rubella antibodies in human sera, enhancing the diagnostic capabilities of immunoassays without the need for detergents.
Implementation Method 1
The antigens further contain two disulfide-bridges, i.e. they contain the region from the disulfide bridge Cys 225-Cys 235 to Cys 349-Cys 352
Implementation Method 2
with specific disulfide bridge combinations (e.g., Cys 225-Cys 235 to Cys 349-Cys 352) stabilized by oxidative refolding
Data Source
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AI summary
The invention relates to soluble Rubella El antigens and variants of these antigens. The antigens comprise amino acids 201 to 432 or 169 to 432 and are lacking amino acids 453 to 481 as well as at least the amino acids 143 to 164. They further contain a region spanning two disulfide-bridges. The invention also relates to a recombinant DNA molecule encoding said Rubella E1 antigens, the expression of Rubella E1 antigens as chaperone fusion proteins and their use in a method of detecting antibodies against Rubella in a sample.