Oxide-Responsive Protein Nanocapsules for Reversible Cargo Release
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Solution Overview
Problem
Existing lumazine synthase cages from Aquifex aeolicus (AaLS) are extremely stable and require harsh conditions to disassemble, making it difficult to package and release cargo molecules at arbitrary timing and location.
Innovation Solution
Engineered AaLS variants with specific mutations, such as cysteine or cysteine orthologs, non-negatively charged and non-hydrophobic amino acids, and histidine, allow for oxide-dependent morphology changes, enabling reversible conformational shifts between closed and open forms in response to oxides like phosphates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If wildtype AaLS is used, then cage stability is maintained, but cargo loading and release becomes difficult due to extremely stable assembly requiring harsh disassembly conditions
Solution Approach 1:
The patent applies dynamics by making the protein cage conformation changeable in response to environmental cues. Engineered AaLS variants with specific mutations (e.g., R21C, E32H, D36H, I125H) can reversibly transition between closed and open conformations upon addition or removal of metal ions, enabling dynamic control over cargo encapsulation and release while maintaining overall cage stability
Solution Approach 2:
The patent employs parameter changes by utilizing metal ion concentration as a controllable parameter to trigger conformational changes. The engineered variants respond to specific metal ions (Ca2+, Mn2+, Zn2+) by changing their conformational state, allowing precise control of cargo loading and release through simple addition or removal of these ions under mild physiological conditions
2Ease of operation
If harsh conditions are applied to disassemble AaLS, then cargo release is achieved, but cargo protein tolerance is compromised
Solution Approach 1:
The patent replaces harsh mechanical/chemical disassembly methods with a biochemical signaling mechanism. Instead of using denaturing agents like guanidine hydrochloride or extreme pH conditions, the engineered variants respond to specific metal ion concentrations to trigger controlled conformational changes, enabling cargo release under mild physiological conditions that preserve cargo protein integrity
3Ease of operation
If pH ≥8 is used to induce morphology change, then release of native guest enzyme is achieved, but applicability to foreign cargo is limited
Solution Approach 1:
The patent achieves universality by engineering AaLS variants that respond to metal ions rather than pH changes. This metal ion-responsive mechanism is more versatile and compatible with a broader range of cargo molecules, including foreign proteins that may be sensitive to alkaline conditions. The same engineered variants can encapsulate both native and foreign cargo through this universal metal ion-triggered conformational change mechanism
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 engineered AaLS variants can change conformation from closed to open forms upon oxide removal, allowing access and release of macromolecules, and vice versa upon oxide addition, facilitating controlled encapsulation and release of cargo molecules under mild physiological conditions.
Implementation Method 1
AaLS variants... that change the conformation from closed to open forms and vice versa in response to oxides
Data Source
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Figure 5(a)~6(b)
AI summary
The present invention provides protein cages, formed by novel variants of lumazine synthase from Aquifex aeolicus (AaLS), that reversibly change the open-close conformation in response to oxides. This controlled open-close characteristic of the protein cages of the invention provides methods for packaging and release of guest cargo objects under mild physiological conditions.