Oxidative E. Coli Cytoplasm for Disulfide-Bonded Protein Expression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bacterial hosts lack the ability to form disulfide bonds in the cytosol, limiting the expression of proteins with disulfide bonds, which are crucial for stability and function, and existing mutations in bacterial hosts have yielded limited success in promoting disulfide bond formation.
Innovation Solution
Genetically engineer E. coli strains to lack thioredoxin reductase, thioredoxin 1, and glutathione reductase activities while overexpressing a mutated AhpC protein with glutathione reductase activity and a cytosolic disulfide isomerase, such as DsbC, to create an oxidative cytoplasm that supports disulfide bond formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bacterial hosts are used for protein expression, then the host is easy to culture and maintain, but the host cannot form disulfide bonds in the cytosol, limiting protein stability and function
Solution Approach 1:
The patent applies parameter changes by modifying the redox state of the cytosol from reducing to oxidizing. This is achieved through multiple genetic modifications: deleting trxB (thioredoxin reductase) and gor (glutathione reductase) genes to eliminate reducing pathways, and overexpressing DsbC (disulfide isomerase) and altered AhpC (peroxiredoxin) to create an oxidizing environment that enables disulfide bond formation in the cytosol
Solution Approach 2:
The patent extracts and removes the reductive pathways (trxB and gor genes) that prevent disulfide bond formation. By deleting these genes, the harmful reducing environment is eliminated, allowing the cytosol to support disulfide-bonded protein expression
2Reliability
If mutations are introduced to disrupt reductive pathways, then disulfide bond formation is promoted, but the success has been limited and protein yield remains low
Solution Approach 1:
The patent combines multiple modifications into a integrated system: deletion of trxB and gor genes to eliminate reductive pathways, overexpression of DsbC for disulfide isomerase activity, and expression of altered AhpC for additional oxidizing capacity. This combination creates a synergistic oxidizing environment that both enables disulfide bond formation and achieves high protein yields
Solution Approach 2:
The patent creates a composite redox system by integrating multiple enzymatic components (DsbC, AhpC) and eliminating reductive pathways. This composite approach builds upon previous mutant strains like Shuffle (which only deleted trxB) by adding gor deletion and altered AhpC expression, creating a more comprehensive oxidizing cytosol that achieves superior protein production
3Reliability
If the cytosol is made oxidative to enable disulfide bonds, then protein stability improves, but the complexity of genetic modifications increases
Solution Approach 1:
The patent segments the redox system into distinct functional components: eliminating reductive pathways (trxB, gor deletions) as one segment, and establishing oxidative pathways (DsbC, AhpC overexpression) as another segment. This segmentation allows systematic control and optimization of the redox environment while managing genetic modification complexity through modular approaches
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 engineered E. coli strains significantly enhance the yield of disulfide-bonded proteins, achieving higher production levels compared to previous mutant strains like Shuffle.
Implementation Method 1
a mutated AhpC protein having glutathione reductase activity
Implementation Method 2
a cytosolic prokaryotic disulfide isomerase
Implementation Method 3
create an oxidative cytoplasm that supports disulfide bond formation
Data Source
AI summary
This disclosure provides an E. coli strain, which lacks thioredoxin reductase activity encoded by trxB and thioredoxin 1 activity encoded by trxA, and glutathione reductase activity encoded by gor. Said E. coli strain expresses a mutated AhpC protein having glutathione reductase activity and a cytosolic prokaryotic disulfide isomerase. The E. coli strain has an oxidative cytosol and can be used to efficiently produce proteins having disulfide bonds.