Mutant AraB Promoter for High Yield Inducible Expression
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Solution Overview
Problem
The existing arabinose inducible expression systems, such as those based on the wild type araB promoter, are not strong enough for optimal protein yield, leading to increased metabolic burden on host cells and uncontrolled constitutive expression, which can be detrimental to cell growth and viability.
Innovation Solution
A mutant araB promoter with a consensus nucleic acid sequence is developed, operably linked to an AraC transcription factor binding region, enhancing protein yield and providing tightly regulated, inducible expression when linked to a coding region of interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wild type araB promoter is used, then the expression is tightly regulated and inducible, but the protein yield is insufficient for optimal production
Solution Approach 1:
The patent applies parameter changes by modifying the araB promoter sequence to create a mutant version with altered transcriptional properties. Specifically, nucleotide substitutions were introduced in the -10 and -35 regions of the promoter to enhance RNA polymerase binding affinity, thereby increasing transcription efficiency and protein yield while preserving inducibility through AraC regulation
Solution Approach 2:
The patent creates a composite promoter structure by combining the mutated araB promoter sequence with the AraC transcription factor binding region. This composite system integrates the enhanced transcriptional strength of the mutant promoter with the tight regulatory control of AraC, achieving both high protein yield and reliable inducible expression
2Productivity
If multi-copy plasmids are used to increase protein production, then the protein yield increases, but the metabolic burden on the cell increases and growth rate decreases
Solution Approach 1:
The patent changes the promoter strength parameter to create a strong promoter that can drive high-level protein expression from single-copy or low-copy plasmids. This eliminates the need for multi-copy plasmids, thereby maintaining cellular growth rate while achieving high protein production through enhanced transcriptional efficiency of the mutant araB promoter
3Productivity
If strong promoters are used to increase protein production, then the protein yield increases, but the expression becomes uncontrolled and constitutive, harming cell growth and viability
Solution Approach 1:
The patent constructs a composite expression system by fusing the strong mutant araB promoter with the AraC transcription factor binding region. This composite design ensures that while the promoter provides strong transcriptional drive for high protein yield, the AraC binding region maintains tight regulatory control, allowing inducible expression that does not harm cell growth when uninduced
Solution Approach 2:
The patent implements feedback control through the AraC transcription factor, which senses the presence of L-arabinose and adjusts transcription accordingly. When L-arabinose is absent, AraC represses transcription; when L-arabinose is present, AraC activates transcription. This feedback mechanism provides precise control over the strong promoter, preventing constitutive expression while enabling high-level production when needed
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 mutant araB promoter significantly increases protein yield compared to the wild type, reducing metabolic burden on host cells and allowing for controlled expression, making it suitable for low-cost peptide/protein production, especially for small bioactive peptides.
Implementation Method 1
Genetic information encoded in DNA molecules is expressed by a series of steps involving transcription of DNA into mRNA and the subsequent translation of the mRNA into polypeptides or proteins. The expression of the encoded information to form polypeptides is initiated at the promoter site, a region on the DNA molecule to which RNA polymerase binds and initiates transcription.
Implementation Method 2
The mutant promoter, when operably-linked to an AraC transcription factor binding region, exhibits tightly regulated and inducible expression in an AraC+ microbial host cell.
Data Source
AI summary
An L-arabinose inducible expression system comprising a mutant arabinose promoter. This system exhibits an increase in heterologous protein production upon induction with L-arabinose and comprises a mutant araB promoter and an AraC transcription binding region. This system retains the tight regulatory control characteristic of the wild type arabinose operon.