rpoC Gene Mutations for Enhanced Protein Expression
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Solution Overview
Problem
Current methods for improving protein production in microbial hosts, such as classical strain improvement techniques, face limitations like labor intensity, plasmid instability, and integration issues, which hinder efficient production of desired proteins in Gram-positive bacterial cells.
Innovation Solution
Modification of Gram-positive bacterial cells with mutations in the rpoC gene encoding a variant RNA-polymerase β′-subunit polypeptide, either integrated into the chromosome or carried on an extrachromosomal plasmid, to enhance protein production, specifically through mutations like methionine to isoleucine substitution, arginine to histidine substitution, and aspartic acid to glycine substitution, leading to increased expression of proteins like amylases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If classical strain improvement methods (multiple rounds of mutagenesis and selection) are used to improve protein production, then productivity of host microbial strains is improved, but labor intensity increases significantly
Solution Approach 1:
The invention changes the genetic parameter of the host cell by introducing specific mutations in the rpoC gene encoding RNA polymerase beta'-subunit. This single genetic modification alters the transcriptional machinery of the cell, enabling sustained high-level protein production without requiring multiple iterative mutagenesis rounds and selection processes, thereby dramatically reducing labor intensity and time investment.
2Productivity
If multiple copies of expression vectors are introduced into host cells to increase protein production, then productivity is improved, but plasmid stability decreases and plasmids are lost during cultivation
Solution Approach 1:
The invention extracts the protein production enhancement function from the plasmid-based expression system and transfers it to the host cell's chromosomal RNA polymerase enzyme through rpoC gene mutation. This eliminates the need for multiple plasmid copies, thereby maintaining plasmid stability and preventing plasmid loss during cultivation while still achieving high-level protein production.
3Productivity
If multiple copies of a gene are integrated into the host chromosome to improve protein production, then productivity is improved, but host cell stability decreases
Solution Approach 1:
Instead of increasing gene copy number in the chromosome, the invention changes the functional parameter of the RNA polymerase enzyme through rpoC gene mutation. This single locus modification alters the transcriptional activity of the entire genome, enabling high-level protein production from single-copy genes without causing chromosomal instability or compromising host cell stability.
4Productivity
If RNA polymerase beta'-subunit mutations are introduced to enhance protein expression, then protein production is improved, but genetic competency may be affected
Solution Approach 1:
The invention introduces specific point mutations in the rpoC gene that selectively enhance transcriptional activity for protein expression while preserving the RNA polymerase's essential functions for cell viability and genetic competency. The mutations are designed to optimize catalytic efficiency without disrupting the enzyme's ability to maintain normal cellular processes including DNA replication, repair, and transformation.
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 modified bacterial cells demonstrate significantly increased protein production, with enhanced expression levels of proteins such as amylases, overcoming the limitations of traditional methods by stabilizing protein production and improving genetic competency.
Implementation Method 1
RNA-polymerase (hereinafter, 'RNAP') is one of the most central transcriptional regulatory hubs... The RNAP core enzyme is comprised of a (alpha), 3 (beta), and beta' (beta prime) subunits... modified Gram positive bacterial cells producing increased amounts of one or more protein(s) of interest... wherein the modified bacterial cell comprises at least one mutation in a rpoC gene encoding a variant RNA-polymerase beta'-subunit polypeptide
Data Source
AI summary
The present disclosure is generally related to modified Gram positive bacterial cells producing increased amounts of one or more protein(s) of interest and modified Gram positive bacterial cells having increased genetic competency. Thus, certain embodiments of the disclosure are directed to modified Gram positive bacterial cells expressing an increased amount of a protein of interest, relative to an unmodified (parental) Gram positive bacterial cell expressing the same protein of interest, wherein the modified bacterial cell comprises at least one mutation in a rpoC gene encoding a variant RNA-polymerase (RNAP) β′-subunit polypeptide. In certain embodiments, the rpoC gene encoding the variant β′-subunit polypeptide is integrated into the chromosome of the modified cell. In other embodiments, the rpoC gene encoding the variant β′-subunit polypeptide is comprised on an extrachromosomal plasmid introduced into the modified cell. In other embodiments, the disclosure is directed to competent Bacillus host cells comprising at least one copy of a nucleic acid construct encoding a modified rpoC polypeptide comprising 90% sequence identity to SEQ ID NO: 8 and an aspartic acid to glycine substitution at position 796 of SEQ ID NO: 8, wherein the polynucleotide encoding the rpoC polypeptide is foreign to the Bacillus host cell that was non-competent prior to the introduction of the first nucleic acid construct.