Genetically Modified E. coli Cytoplasm for Disulfide Bond Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing proteins with multiple disulfide bonds in bacteria are inefficient, leading to degradation or insolubility in E. coli due to the reducing cytoplasm, which complicates the production of biotechnologically important proteins like tissue plasminogen activator (tPA), resulting in high production costs and limited availability.
Innovation Solution
Genetically modify prokaryotic host cells to shift their cytoplasmic redox status to a more oxidative state by reducing reductase activity and introducing catalysts for disulfide bond formation and isomerization, such as thioredoxin or glutaredoxin variants, to facilitate proper folding and stability of disulfide-bonded proteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If proteins with disulfide bonds are expressed in E. coli cytoplasm, then production cost is reduced and availability is improved, but the proteins become degraded or insoluble due to the reducing cytoplasm environment
Solution Approach 1:
The patent changes the redox potential parameter of the E. coli cytoplasm from a reducing state to an oxidizing state through genetic modifications (deletion of trxB and gor genes, overexpression of DsbC). This parameter change enables disulfide bond formation in the cytoplasm, allowing proteins to fold correctly and remain stable, thereby resolving the contradiction between using inexpensive bacterial hosts and maintaining protein stability.
Solution Approach 2:
The patent introduces DsbC as an intermediary enzyme that catalyzes disulfide bond formation and isomerization in the cytoplasm. This intermediary overcomes the reducing environment barrier, enabling proper protein folding and stability in the cytoplasmic compartment while maintaining the benefits of bacterial expression systems.
2Reliability
If alternative expression strategies such as export to periplasm are used, then protein stability is improved through disulfide bond formation, but the process becomes laborious requiring recloning in other vectors
Solution Approach 1:
The patent extracts the disulfide bond formation capability (DsbC enzyme) from its native periplasmic location and places it in the cytoplasm. This extraction eliminates the need for periplasmic targeting signals and complex recloning procedures, simplifying the expression process while maintaining protein stability through cytoplasmic disulfide bond formation.
Solution Approach 2:
The modified E. coli cytoplasm becomes a universal expression system that can produce proteins requiring disulfide bonds without needing separate periplasmic expression systems. The cytoplasm acquires the multi-functionality of both being the primary protein synthesis location and providing oxidizing conditions for disulfide bond formation, eliminating the need for alternative expression strategies.
3Stability of the object's composition
If the cytoplasm is maintained in a reducing state with thioredoxins and glutathione, then normal cellular functions are preserved, but disulfide bonds cannot form in cytosolic proteins
Solution Approach 1:
The patent segments the redox systems by selectively deleting specific reductase genes (trxB and gor) while maintaining other cellular functions. This segmentation creates a compartmentalized redox environment where the cytoplasm becomes oxidizing for disulfide bond formation while other cellular processes continue normally, resolving the contradiction between maintaining cellular redox balance and enabling disulfide bond formation.
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 enables efficient production of recombinant proteins with multiple disulfide bonds in the cytoplasm of modified bacterial cells, improving yield and biological activity, and reducing production costs by allowing for cheaper manufacturing of therapeutic proteins like tPA.
Implementation Method 1
the oxidation of cysteine thiols in cytoplasmic proteins is strongly disfavored for both thermodynamic and kinetic reasons
Implementation Method 2
The thiol-disulfide redox potential of the cytoplasm is too low to provide a sufficient driving force for the formation of stable disulfides
Implementation Method 3
disulfide bond formation in gram-negative bacteria does require the presence of a protein catalyst, DsbA
Data Source
AI summary
The invention provides composition and methods for producing proteins of interest which comprise at least one disulfide bond, include proteins which in their mature form do not contain disulfide bonds, but whose precursor molecule contained at least one disulfide bond. The methods employ a host cell modified to more efficiently produce properly folded disulfide bond containing proteins. The host cells generally contain a mutation in one or more reductase genes, and can be further genetically modified to increase their growth rate, and are further optionally modified to increase the expression of a catalyst of disulfide bond formation. Host cells, methods for u sing such to produce proteins of interest, proteins of interest produced by these methods are within the scope of the invention.