Inducible Coexpression Vectors for Homogeneous Protein Expression
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Solution Overview
Problem
Current inducible bacterial protein expression systems face challenges in coexpressing multiple gene products due to compatibility issues, 'crosstalk' effects, and metabolic regulation, leading to suboptimal expression and production of proteins that require tight control or have poor solubility.
Innovation Solution
Development of coordinated bacterial coexpression systems using compatible homogenously inducible promoter systems on separate expression constructs activated by different inducers, such as L-arabinose and propionate, to achieve controlled induction and improved compatibility, allowing for the expression of multimeric proteins and proteins forming disulfide bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wild-type E. coli lac and ara systems are used for inducible protein expression, then individual proteins can be expressed, but homogeneous induction throughout the entire growth culture population cannot be achieved due to the all-or-none phenomenon
Solution Approach 1:
The patent removes the inducer-dependent transport proteins (lacY and araE) from the system by using strains with deletions in these genes. This extraction of the problematic feedback mechanism eliminates the all-or-none phenomenon while preserving the inducible expression capability through alternative inducer uptake mechanisms.
Solution Approach 2:
The patent introduces alternative inducer uptake mechanisms that are not dependent on the problematic transport proteins. By using intermediaries such as passive diffusion or alternative transporters, the system achieves homogeneous induction without the positive feedback loop that causes the all-or-none effect.
2Adaptability or versatility
If multiple inducible promoters are used for coexpression of multiple gene products, then different proteins can be expressed simultaneously, but compatibility issues and crosstalk effects occur between the promoter systems
Solution Approach 1:
The patent divides the coexpression system into separate, independent promoter modules (lac promoter and ara promoter) that can be controlled independently. By segmenting the control mechanisms and removing the feedback loops that cause crosstalk, each promoter system operates autonomously without interfering with the other, enabling reliable coexpression of multiple gene products.
3Productivity
If inducer concentration is increased to overcome the all-or-none phenomenon, then a higher proportion of cells enter high-expression mode, but uncontrolled positive feedback occurs leading to excessive inducer accumulation
Solution Approach 1:
The patent extracts the problematic inducer-dependent transport proteins (lacY and araE) from the system. By removing these proteins that create the positive feedback loop, the system can achieve high expression levels without the uncontrolled accumulation of inducer that occurs in wild-type systems.
Solution Approach 2:
The patent eliminates the positive feedback mechanism by removing the inducer-dependent transport proteins. Without these proteins, increased inducer concentration does not lead to increased transport and subsequent uncontrolled expression, thereby providing reliable control over expression levels while maintaining productivity.
Data Source
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AI summary
The present invention provides expression vectors for use in an inducible coexpression system, capable of controlled induction of expression of each gene product.