Modified Sigma Factor A Enhances Lysine Yield
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Solution Overview
Problem
Current methods struggle to enhance L-lysine producibility in microorganisms like Corynebacterium without inhibiting host cell growth, limiting the production efficiency and cost-effectiveness of L-lysine production.
Innovation Solution
A modified RNA polymerase sigma factor A (SigA) polypeptide with specific amino acid substitutions is introduced into Corynebacterium microorganisms, enhancing L-lysine production by upregulating transcriptional activity, thereby improving yield and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If random mutagenesis of SigA is performed to enhance L-lysine producibility, then L-lysine production increases, but host cell growth is inhibited
Solution Approach 1:
The invention applies parameter changes by modifying specific amino acid residues in the SigA polypeptide sequence. Through site-directed mutagenesis at positions 68, 103, 136, 170, 230, 268, 281, 381, 414, 451, 479, and 483, the patent optimizes the transcriptional activity of SigA to enhance L-lysine production while maintaining host cell growth capability. This targeted approach contrasts with random mutagenesis by precisely adjusting critical parameters in the protein sequence.
Solution Approach 2:
The invention applies local quality by making specific localized modifications at particular amino acid positions within the SigA polypeptide rather than random throughout the sequence. The mutations are concentrated at key regions involved in promoter recognition and transcription initiation, such as positions 68, 103, and 136, which are critical for RNA polymerase binding and transcriptional activation. This localized optimization allows enhanced L-lysine production without globally disrupting cellular functions.
2Productivity
If transcriptional activity is upregulated to increase L-lysine yield, then production efficiency improves, but cellular metabolic balance is disrupted
Solution Approach 1:
The invention applies partial action by implementing moderate transcriptional upregulation through controlled amino acid substitutions in SigA. Rather than maximizing transcriptional activity to extreme levels, the patent uses specific mutations (e.g., D68G, A103V, D136G) that provide optimal enhancement of L-lysine production while maintaining sufficient transcription of other essential genes. This balanced approach prevents metabolic disruption while achieving high productivity.
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 SigA polypeptide significantly increases L-lysine producibility in Corynebacterium strains, leading to higher yields and economic advantages in industrial production without compromising host cell growth.
Implementation Method 1
The RNA polymerase used in the transcription step in microorganisms is a macromolecule consisting of 5 small subunits, i.e., two α factors, one β factor, one β' factor, and one ω factor, and its holoenzyme is indicated by α 2 ββ'ω. Sigma (σ) factors, together with the holoenzyme, are essential factors for the initiation step of transcription
Data Source
AI summary
The present disclosure relates to a novel modified RNA polymerase sigma factor A (SigA) polypeptide; a polynucleotide encoding the same; a microorganism containing the polypeptide; and a method for producing L-lysine using the microorganism.