Soluble Rubella E1 Antigen via Segmentation and Chaperone Fusion
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Solution Overview
Problem
Current methods for producing rubella antigens, particularly the E1 protein, face challenges such as low yield, insolubility, and complexity in oxidative refolding due to the protein's cysteine-rich nature, making it difficult to achieve high solubility and immunoreactivity for serological assays.
Innovation Solution
A soluble rubella E1 antigen variant is developed by deleting the transmembrane region, C-terminal anchor segment, and specific amino acid sequences, while maintaining critical disulfide bridges, allowing for recombinant expression and refolding into a soluble, immunoreactive conformation using chaperone fusion proteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the complete rubella E1 protein is produced using current methods, then the antigen contains all immunoreactive regions, but the protein exhibits low solubility and requires complex oxidative refolding due to its cysteine-rich nature
Solution Approach 1:
The E1 protein is divided into two separate polypeptide chains: Chain A contains the N-terminal region with immunoreactive epitopes (amino acids 1-200), while Chain B contains the C-terminal region with disulfide bridges (amino acids 201-481). This segmentation allows each chain to be expressed and folded independently, avoiding the solubility and refolding issues of the full-length protein while preserving all necessary immunoreactive regions.
Solution Approach 2:
A fusion partner (such as GST, MBP, or Trx) is used as an intermediary to facilitate the expression and solubility of the E1 antigen chains. The fusion partner acts as a mediator that enhances solubility during expression, and can be subsequently removed to yield the native E1 antigen structure.
2Reliability
If the complete E1 protein is expressed as a single polypeptide, then all disulfide bridges are present, but the protein forms insoluble aggregates and requires complex refolding procedures
Solution Approach 1:
The protein is segmented into two chains that are expressed separately. Chain A (amino acids 1-200) and Chain B (amino acids 201-481) can be expressed independently as soluble proteins, avoiding aggregate formation. The disulfide bridges are formed within each chain during independent folding, ensuring integrity without requiring complex refolding of the entire protein.
Solution Approach 2:
The problematic region causing aggregation (the complete single polypeptide structure with all disulfide bridges) is extracted and replaced by two separate polypeptide chains. This extraction of the aggregation-prone configuration allows high-yield expression while maintaining all necessary disulfide bridges in their respective chains.
3Quantity of substance
If traditional antigen production methods are used, then the full-length E1 protein is obtained, but the process involves low yield and time-consuming oxidative refolding
Solution Approach 1:
By segmenting the E1 protein into two separately expressible chains, the refolding process is simplified. Each chain folds independently with its disulfide bridges forming during expression, eliminating the need for time-consuming oxidative refolding of the complete protein. This increases both yield and reduces processing time.
Solution Approach 2:
The disulfide bridges are formed preliminarily during the expression and folding of each individual chain, before the chains are combined. This preliminary formation of disulfide bonds in separate, soluble chains avoids the need for subsequent oxidative refolding steps, saving time and increasing yield.
Data Source
AI summary
A soluble rubella E1 antigen variant is disclosed that comprises amino acids 334-409 of the native rubella E1 peptide, but lacks the C-terminal end and at least the transmembrane region and the anchor segment as well as at least the amino acids 143 to 164. Also described is a recombinant DNA molecule encoding the rubella E1 antigen variants which are recombinantly expressed as a chaperone fusion protein, refolded into a soluble and immunoreactive conformation, and further used for the serological detection of anti-rubella antibodies. In addition, also disclosed is a method for the detection, determination and quantification of anti-rubella antibodies of IgG and/or IgM subclass in a sample wherein the rubella E1 antigen is used as a capture reagent and/or binding partner for the antibodies.