Recombinant Yeast Host Cells for Heterologous Fe-S Cluster Protein Expression
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Solution Overview
Problem
Current methods fail to achieve high levels of expression for heterologous iron-sulfur cluster proteins in yeast cells, which are essential for enhancing biosynthetic pathways like those for isobutanol, 2-butanol, and 2-butanone production, due to challenges in forming and loading iron-sulfur clusters into apo-proteins.
Innovation Solution
Engineering recombinant yeast host cells with reduced expression of endogenous iron-sulfur cluster proteins, specifically disrupting genes encoding proteins like dihydroxy-acid dehydratase and isopropylmalate dehydratase, to enhance the activity of heterologous iron-sulfur cluster proteins such as fungal or plant 2Fe-2S dihydroxy-acid dehydratases and propanediol dehydratase reactivases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If endogenous Fe-S cluster proteins are highly expressed in yeast cells, then the host cell maintains normal metabolic functions, but the expression level of heterologous Fe-S cluster proteins remains too low for commercial use
Solution Approach 1:
The patent extracts the problematic endogenous Fe-S cluster proteins from the yeast cell system by inactivating their encoding genes. This removal eliminates the competition for limited Fe-S clusters, allowing heterologous Fe-S proteins to receive sufficient clusters for activity. The principle is applied by identifying and inactivating specific endogenous Fe-S protein genes that compete with heterologous proteins for Fe-S cluster availability.
Solution Approach 2:
The patent changes the expression parameter of endogenous Fe-S cluster proteins from high to reduced levels through gene inactivation. This parameter change resolves the contradiction by creating an environment where Fe-S clusters are preferentially available to heterologous proteins, thereby increasing their expression and activity levels to commercially useful ranges.
2Productivity
If Fe-S clusters are made available for heterologous protein loading, then heterologous protein activity increases, but endogenous Fe-S dependent pathways may be compromised
Solution Approach 1:
The patent converts the harmful effect of endogenous Fe-S protein competition into a benefit by selectively inactivating specific endogenous Fe-S protein genes. This strategic inactivation reduces Fe-S cluster demand from endogenous proteins, thereby increasing availability for heterologous proteins while maintaining essential metabolic functions through selective gene targeting rather than blanket suppression.
3Productivity
If gene disruption is used to reduce endogenous Fe-S protein expression, then heterologous protein expression improves, but the genetic modification process becomes more complex
Solution Approach 1:
The patent segments the complex problem of enhancing heterologous Fe-S protein expression into manageable steps: (1) identification of specific endogenous Fe-S protein genes to inactivate, (2) targeted gene disruption using standard molecular biology techniques, and (3) verification of Fe-S cluster availability to heterologous proteins. This segmentation makes the genetic engineering process more systematic and controllable.
Data Source
AI summary
Yeast strains were engineered that have increased activity of heterologous proteins that require binding of an Fe—S cluster for their activity. The yeast strains have reduced activity of an endogenous Fe—S protein. Activities of heterologous fungal or plant 2Fe-2S dihydroxy-acid dehydratases and Fe—S propanediol dehydratase reactivase were increased for increased production of products made using biosynthetic pathways including these enzymes, such as valine, isoleucine, leucine, pantothenic acid (vitamin B5), isobutanol, 2-butanone and 2-butanol.