RhtB Protein Variants for Enhanced O-Phosphoserine Export
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Solution Overview
Problem
Current methods for producing L-cysteine require high amounts of O-phosphoserine (OPS) to achieve high yields, and existing transporters do not efficiently export OPS from OPS-producing strains, limiting cysteine production.
Innovation Solution
Development of RhtB protein variants with enhanced OPS export activity, which are used to create OPS-producing microorganisms that effectively secrete OPS, thereby increasing OPS productivity and subsequent cysteine production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing transporters are used to export OPS from OPS-producing strains, then OPS can be secreted from cells, but the export efficiency is insufficient and limits cysteine production yield
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of the RhtB transporter protein to create variants with enhanced OPS export activity. Specific amino acid substitutions (e.g., F13Y, F13W, L16F, L16Y, L16W, Q17L, Q17M, Q17F, Q17Y, Q17W, Q22L, Q22M, Q22F, Q22Y, Q22W, Q26L, Q26M, Q26F, Q26Y, Q26W) were introduced to improve the transporter's ability to export OPS from cells, thereby resolving the contradiction between adequate export function and insufficient export efficiency.
2Productivity
If high amounts of OPS are required to achieve high cysteine yields, then cysteine production can be increased, but the dependency on large OPS quantities limits process efficiency
Solution Approach 1:
The patent modifies the RhtB transporter protein parameters (amino acid sequence) to create variants with enhanced OPS export activity. This allows the system to achieve high cysteine production yields with improved OPS utilization efficiency, reducing the quantity of OPS required while maintaining or increasing cysteine productivity.
3Quantity of substance
If RhtB expression is enhanced in OPS-producing strains, then OPS concentration increases, but further improvement is needed to achieve higher cysteine yields
Solution Approach 1:
The patent introduces amino acid substitutions in the RhtB protein sequence to create variants with superior OPS export capability compared to wild-type RhtB. These parameter changes in the transporter protein enable more efficient OPS secretion, allowing the system to convert higher OPS concentration into proportionally higher cysteine yields, thus resolving the limitation of achieving higher cysteine productivity.
Data Source
AI summary
The present invention relates to an RhtB (homoserine/homoserine lactone export transporter) protein variant having an enhanced ability to export O-phosphoserine (OPS) that is a precursor of L-cysteine, a polynucleotide encoding the protein, a vector comprising the polynucleotide, an OPS-producing microorganism comprising the protein variant, a method of producing O-phosphoserine using the microorganism, and a method for preparing cysteine or its derivatives, which comprises reacting O-phosphoserine, produced by the method above, with a sulfide in the presence of O-phosphoserine sulfhydrylase (OPSS) or a microorganism that expresses OPSS.