Engineered Fluorescent Proteins with Cell-Permeable Surface Charges
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Solution Overview
Problem
Current fluorescent proteins like GFP face limitations in cell permeability, which hinders their use as therapeutic and diagnostic tools due to the challenge of breaching the plasma membrane barrier.
Innovation Solution
Engineered fluorescent proteins with positively charged amino acid substitutions on the exterior surface, specifically at positions 17, 19, 21, 111, and 124, to render them cell-permeable, allowing them to enter cells without the need for transfection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GFP is used as a fluorescent marker, then fluorescent activity is retained, but cell permeability is poor due to the plasma membrane barrier
Solution Approach 1:
The patent applies parameter changes by modifying the charge distribution on the GFP surface through site-directed mutagenesis. Specifically, negatively charged residues (glutamate and aspartate) are replaced with positively charged residues (arginine and lysine) at positions 17, 19, 21, 111, and 124. This changes the electrostatic parameters of the protein surface, enabling it to interact with and permeate through the plasma membrane while preserving fluorescent activity.
Solution Approach 2:
The patent applies local quality by making specific localized changes to the GFP molecule rather than global modifications. The amino acid substitutions are targeted at specific positions (17, 19, 21, 111, and 124) on the protein surface, creating localized positive charge regions that facilitate membrane interaction while leaving the overall fluorescent structure intact.
2Ease of operation
If transfection is used to deliver GFP into cells, then cell permeability is achieved, but the process complexity increases
Solution Approach 1:
The patent applies self-service by engineering GFP to possess intrinsic cell-permeable properties through its modified charge distribution. The protein autonomously achieves membrane permeability without requiring external transfection machinery, liposomes, or complex delivery systems. The cationic surface residues enable the GFP to self-interact with and traverse the plasma membrane directly.
3Ease of operation
If amino acid substitutions are made to improve cell permeability, then fluorescent protein can enter cells, but the risk of losing fluorescent activity increases
Solution Approach 1:
The patent applies partial action by making targeted amino acid substitutions at specific positions (17, 19, 21, 111, and 124) rather than comprehensive modifications throughout the protein. This selective approach provides sufficient cell permeability while minimizing disruption to the fluorescent chromophore and overall protein structure.
Solution Approach 2:
The patent applies copying by creating multiple variant versions of GFP with different combinations of amino acid substitutions at the specified positions. These variants can be screened and selected to optimize the balance between cell permeability and fluorescent activity, effectively copying and testing different configurations to find the optimal solution.
Data Source
AI summary
This invention relates to methods and compositions for designing novel fluorescent proteins, preferably to a green fluorescent proteins (GFP). The engineered GFPs are modified by substituting negatively charged amino acids with positively charged amino acids on the exterior of the protein making the protein cell permeable. The ability of the engineered fluorescent proteins to permeate cells obviates the need for transfections, allowing these novel proteins to be used in numerous biological applications.