Covalently Circularized Nanodiscs for Uniform Membrane Protein Studies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nanodiscs have limited size range and variability, which hinders their utility in structural and functional studies of membrane proteins due to size heterogeneity and instability, particularly in crystallization and NMR analysis.
Innovation Solution
The development of covalently circularized nanodiscs using loopable membrane scaffold proteins with circularization domains and amphipathic alpha helix domains, allowing for the formation of nanodiscs up to 80 nm in diameter with uniform size and polygonal shapes, enhancing stability and crystallization potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional linear membrane scaffold proteins are used to form nanodiscs, then the nanodiscs can be assembled, but the size range is limited to 7-17 nm and size uniformity is poor
Solution Approach 1:
The patent employs nested circularization by incorporating multiple circularization domains within the membrane scaffold protein sequence. These domains enable the protein to fold back and form covalent loops, creating a nested structure that constrains the nanodisc to uniform sizes while allowing expansion beyond the conventional 7-17 nm range up to 100 nm diameter.
Solution Approach 2:
The patent changes the structural parameter of the membrane scaffold protein from linear to covalently circularized by introducing circularization domains with specific amino acid sequences. This parameter change enables the formation of stable loops that define precise nanodisc dimensions, achieving both larger size range and improved size uniformity simultaneously.
2Quantity of substance
If larger nanodiscs are formed to accommodate more membrane proteins, then the capacity increases, but size heterogeneity increases and stability decreases
Solution Approach 1:
The nested circularization domains create multiple constraining loops within the scaffold protein that work together to maintain structural integrity. This nested architecture allows the nanodisc to expand in size to accommodate more membrane proteins while the covalent loops prevent aggregation and maintain size homogeneity, thus preserving stability at larger dimensions.
Solution Approach 2:
The patent creates a composite structure by combining the membrane scaffold protein with phospholipid bilayer and membrane proteins within a covalently closed loop. This composite architecture, where the circularized protein forms a stable belt around the lipid bilayer, enables larger nanodiscs to maintain uniformity and stability by distributing mechanical stress across the reinforced circular structure.
3Ease of manufacture
If linear membrane scaffold proteins are used, then the assembly process is simple, but the nanodiscs aggregate and show irregular sizes
Solution Approach 1:
The nested circularization domains are integrated directly into the membrane scaffold protein coding sequence, adding only a few amino acid residues at the N- and C-termini. This minimal modification maintains ease of protein expression and assembly while the resulting covalent loops prevent aggregation by eliminating free ends that would otherwise promote intermolecular interactions.
Solution Approach 2:
The circularization domains act as intermediary elements that mediate the connection between N- and C-termini of the membrane scaffold protein. These intermediary sequences facilitate covalent bond formation that closes the loop, creating a stable structure that resists aggregation while requiring only simple expression and assembly procedures.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Described herein are methods and compositions relating to nanodiscs, e.g., phospholipid bilayers with a proteinaceous belt or border. Further provided herein are loopable membrane scaffold proteins, e.g., for forming nanodiscs.