Functionally Coupled Expression Cassette for Bacterial Protein Production
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Solution Overview
Problem
Current methods for large-scale recombinant production of proteins face challenges in efficiently producing environmentally or therapeutically useful proteins, particularly in linking the expression of a selectable marker protein with the protein of interest in bacterial cells, which is critical for growth or survival, and in efficiently removing metals from contaminated materials.
Innovation Solution
Genetically modified bacterial cells are configured with a chromosomally integrated or cytoplasmic expression cassette that includes a first nucleic acid sequence encoding a protein of interest and a second nucleic acid sequence encoding a selectable marker protein, where the regulatory sequence for the selectable marker also drives the expression of the protein of interest, allowing for 'functionally coupled' expression, and these cells are used to produce proteins such as metal-binding proteins for metal removal from environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate expression systems are used for selectable marker and protein of interest, then selection efficiency is improved, but expression linkage and production efficiency deteriorate
Solution Approach 1:
The patent merges the selectable marker gene and the protein of interest gene into a single expression cassette under one regulatory sequence, creating a functionally coupled system where both genes are expressed together from the same promoter, thereby linking selection efficiency with production efficiency
2Adaptability or versatility
If multiple separate expression cassettes are used, then gene expression control is improved, but system complexity and manufacturing difficulty worsen
Solution Approach 1:
The patent combines multiple gene expression functions into a single integrated expression cassette containing both the selectable marker and protein of interest under one regulatory sequence, reducing the number of separate genetic components while maintaining expression control
Solution Approach 2:
The regulatory sequence in the expression cassette serves multiple functions simultaneously: it drives expression of both the selectable marker and the protein of interest, making it a multi-functional element that controls multiple genes
3Ease of manufacture
If conventional protein production methods are used, then existing infrastructure is utilized, but scalability and large-scale production capability deteriorate
Solution Approach 1:
The expression cassette design allows the system to self-select and self-maintain high-producing strains through the functional coupling mechanism, where the selectable marker automatically selects for cells that are also producing the protein of interest at high levels, eliminating the need for complex external selection processes
Data Source
AI summary
The present invention is based, in part, on our discovery of a way to configure expression cassettes so that the expression of a selectable marker protein, which is critical for the growth or survival of a cell, also results in the expression of a protein of interest in a biological cell. Accordingly, in one aspect, the invention features a genetically modified cell (e.g., a bacterial cell) that includes a chromosomally integrated or cytoplasmic expression cassette that includes a first nucleic acid sequence encoding a protein of interest and a second nucleic acid sequence encoding a selectable marker protein. The regulatory sequence (e.g., the sequence encoding a functional promoter) that drives expression of the required selectable marker protein also drives expression of the protein of interest. For that reason, we may refer to their expression as being “linked” or “functionally couple.”