SpyCatcher-21_A82P Proline Mutation for pH-Responsive Ligation
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Solution Overview
Problem
The original SpyTag/SpyCatcher system lacks stimulus response to environmental changes and is sensitive to modifications, which can affect isopeptide bond formation and ligation efficiency, making amino acid mutations risky and potentially inactivating the protein.
Innovation Solution
A molecular peptide mutant, SpyCatcher-21_A82P, is designed with a proline mutation in the E81-A91 loop to reduce flexibility and introduce stimulus response to pH without affecting isopeptide bond formation, improving ligation efficiency through careful analysis of crystal structures and surface potential modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If amino acid mutations are made to SpyCatcher to improve ligation efficiency or add stimulus response, then functional properties are improved, but protein inactivation risk increases
Solution Approach 1:
The patent applies local quality by introducing a proline mutation at a specific location (residue 82) within the E81-A91 loop region of SpyCatcher. This localized mutation provides pH responsiveness and improved ligation efficiency without disrupting the overall protein structure or other functional regions, thereby avoiding widespread inactivation risk while achieving specific functional enhancements.
Solution Approach 2:
The patent utilizes parameter changes by modifying the chemical properties of a specific amino acid residue (changing from a flexible residue to proline with rigid side chain). This parameter change in the local structural property enables pH stimulus response and improved ligation efficiency while maintaining overall protein stability and function.
2Productivity
If amino acid mutations are made to SpyCatcher to improve ligation efficiency, then ligation efficiency is improved, but the ability to form isopeptide bonds with SpyTag may be affected
Solution Approach 1:
The proline mutation is introduced locally in the E81-A91 loop region, which is distinct from the active site residues (Tyr84, Glu85, Tyr119, Lys120) responsible for isopeptide bond formation. This localized modification improves ligation efficiency through reduced loop flexibility without compromising the chemical functionality of the isopeptide bond formation sites.
Solution Approach 2:
The patent segments the SpyCatcher protein into functional regions: the E81-A91 loop region that provides ligation efficiency through structural rigidity, and the active site residues that maintain isopeptide bond formation capability. This segmentation allows independent optimization of each function without interference between them.
3Productivity
If the SpyCatcher structure is modified to reduce loop flexibility, then ligation efficiency is improved, but surface potential and enzyme activity may be altered
Solution Approach 1:
The proline mutation is confined to a specific local region (E81-A91 loop) and does not extend to surface residues that determine surface potential or active site residues that catalyze isopeptide bond formation. This localized structural modification improves ligation efficiency through reduced flexibility while preserving surface potential and enzymatic activity.
Solution Approach 2:
The patent changes the flexibility parameter of a specific loop region by introducing proline, which has a rigid side chain that reduces conformational flexibility. This localized parameter change improves ligation efficiency without altering the electrostatic surface potential or catalytic parameters of the enzyme active site.
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 mutant SpyCatcher-21_A82P exhibits enhanced ligation efficiency and pH responsiveness, enabling double-enzyme catalysis by adjusting pH or forming a three-enzyme catalytic system through electrostatic interactions, while maintaining isopeptide bond formation capabilities.
Implementation Method 1
The introduction of Pro confers rigidity to the side chain, which in turn reduces the flexibility of E81-A91 loop and stabilizes the interactions between Tyr86 and Glu87 on SpyCatcher-21 and that between Tyr119 and Lys120 on the SpyTag
Implementation Method 2
Tyr119 and Lys120 on SpyTag and Tyr84 and Glu85 on Spycatcher play a crucial role in the formation of isopeptide bonds due to their π-π stacking effect and a salt bridge, respectively
Implementation Method 3
Tyr119 and Lys120 on SpyTag and Tyr84 and Glu85 on Spycatcher play a crucial role in the formation of isopeptide bonds due to their π-π stacking effect and a salt bridge, respectively
Implementation Method 4
The molecular peptide mutant, SpyCatcher-21_A82P, is designed with a proline mutation in the E81-A91 loop to reduce flexibility and introduce stimulus response to pH
Implementation Method 5
The purified protein is dialyzed in a 3,000 Da dialysis bag for 24-26 h
Implementation Method 6
adding IPTG for induction
Implementation Method 7
carrying out ultrasonication
Implementation Method 8
The supernatant is subjected to protein purification in Ni-NTA resin
Data Source
AI summary
The invention relates to a molecular peptide mutant, the amino acid sequence of which is as shown in SEQ ID NO: 1. In the invention, SpyCatcher is designed and modified to obtain a molecular peptide SpyCatcher-21 with stimulus response to pH on the basis of not affecting the formation of isopeptide bonds, and Pro is introduced into a key loop of the SpyCatcher-21 through analysis of the crystal structure to reduce the flexibility of the loop and obtain a mutant SpyCatcher-21_A82P, which can raise ligation efficiency with SpyTag. The SpyCatcher-21_A82P can be used to achieve double-enzyme catalysis according to objective needs by changing the pH of the environment to obtain different degrees of coupling, or obtain a three-enzyme coupled catalytic system through electrostatic interaction with a positively charged enzyme.