Cryo-EM Protein Structure Determination Using Scaffold Proteins
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Solution Overview
Problem
Current methods for determining protein structures, particularly for membrane proteins, face challenges such as the need for large quantities of purified protein, time-consuming and expensive processes, and difficulties in achieving high-resolution structures below 100-kDa molecular mass, especially for asymmetric complexes and proteins that denature at the air-water interface during electron microscopy sample preparations.
Innovation Solution
A method using cryo-electron microscopy that involves tagging target proteins with biotin or biotinylated tags, allowing them to bind with scaffold proteins like streptavidin, enabling single-particle imaging to determine protein structures down to 20 kDa molecular mass without symmetry restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-particle cryo-EM is used to determine protein structures, then resolution can be achieved for membrane proteins without crystallization, but high-resolution structures below 100-kDa molecular mass remain very challenging
Solution Approach 1:
The patent introduces a scaffold protein as an intermediary that binds to the target protein of interest. This scaffold protein has a known structure and serves as a structural framework that enhances the visibility and interpretability of the target protein's structure in cryo-EM images, enabling high-resolution determination of smaller proteins below 100-kDa that would otherwise be difficult to resolve
Solution Approach 2:
The patent segments the protein structure determination problem by separating the target protein of interest from the structural analysis process. By using a scaffold protein with known structure, the method divides the complex structure determination into manageable components, allowing the target protein's structure to be elucidated through computational methods without requiring the entire complex to be resolved at high resolution
2Difficulty of detecting and measuring
If protein adsorption occurs at the air-water interface during sample preparation, then proteins can be visualized in electron microscopy, but protein denaturation occurs reducing sample quality
Solution Approach 1:
The scaffold protein acts as a protective intermediary that shields the target protein from direct contact with the harmful air-water interface. The scaffold protein's known structure and stability allow it to maintain the target protein in a native state during sample preparation, preventing denaturation while still enabling visualization in the electron microscopy grid
Solution Approach 2:
The method applies beforehand cushioning by using the scaffold protein to protect the target protein from denaturing conditions before the actual imaging process. The scaffold protein's structural stability provides a protective framework that prevents the target protein from undergoing conformational changes or denaturation during the sample preparation and imaging processes
3Measurement precision
If X-ray crystallography is used to determine protein structures, then high-resolution structures can be obtained, but large quantities of purified protein are required and the process is time-consuming and expensive
Solution Approach 1:
The patent uses a scaffold protein with a known structure as a template or copy to guide the structural analysis of the target protein. Instead of requiring large quantities of the target protein to be crystallized and analyzed directly, the method uses computational methods to derive the target protein's structure based on the scaffold protein's known structure and the target protein's binding characteristics, significantly reducing the amount of purified protein needed
4Adaptability or versatility
If NMR spectroscopy is used to determine protein structures in solution, then protein structure can be investigated without crystallization, but proteins must be labelled with isotopes and the process is time-consuming and expensive
Solution Approach 1:
The patent replaces the complex NMR spectroscopy process with a computational approach based on cryo-EM image analysis. Instead of requiring isotopic labeling and complex NMR experiments, the method uses computational algorithms to derive protein structures from cryo-EM images of the target protein bound to the scaffold protein, significantly reducing the time and complexity of the structure determination process while maintaining solution-state analysis capabilities
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
Enables the determination of protein structures at lower molecular weights and reduces protein denaturation issues, allowing for the analysis of smaller and asymmetric protein complexes, improving the resolution and efficiency of structure determination.
Implementation Method 1
enabling a resulting target containing the tag to bind a scaffold protein to form a complex between the target protein and the scaffold protein
Implementation Method 2
performing single-particle imaging using cryo-electron microscopy to determine a structure of the target protein
Data Source
AI summary
A method for determining a protein structure using cryo-electron microscopy, including: enabling a target protein to contain a tag; enabling a resulting target containing the tag to bind a scaffold protein to form a complex between the target protein and the scaffold protein; and performing single-particle imaging using the cryo-electron microscopy to determine a structure of the target protein in complex with the scaffold protein. The scaffold protein is any one of streptavidin, avidin, or derivatives thereof. The tag is configured for selectively binding to the scaffold protein. The tag is one selected from the group consisting of: a biotin tag, comprising a biotin; a biotinylated protein or polypeptide tag, comprising a protein sequence and a biotin covalently linked to the protein sequence; a Strep-tag; and a biotinylated or strep-tagged antibody, or antibody Fab fragment, or single-chain antibody.