Cleavable Linkers for Split Fluorescent Protein Quantification
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Solution Overview
Problem
Existing protein quantification techniques face challenges in achieving high spatial and temporal resolution due to the time required for fluorescent protein folding and maturation, which delays the reporting of protein synthesis events, especially at small subcellular scales.
Innovation Solution
A protein quantification technique using a cleavable protein linker that connects a protein of interest to a small fragment of a split fluorescent protein, where the larger fragment is already expressed and folded, allowing for rapid association and fluorescence generation after cleavage, thereby reducing the time between protein translation and fluorescence detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a full-length fluorescent protein is used as a reporter, then the fluorescence signal is strong and detectable, but the folding and maturation time is prolonged (10 minutes), degrading temporal and spatial resolution
Solution Approach 1:
The fluorescent protein is divided into two fragments: a large fragment (GFP1-10) that is pre-expressed and folded in the cell, and a small fragment (GFP11) that is co-translated with the protein of interest. When the cleavable linker is proteolyzed, GFP11 rapidly associates with GFP1-10 to form the functional fluorescent protein. This segmentation allows the majority of the folding and maturation process to occur in advance, reducing the reporting delay to seconds while maintaining strong fluorescence signal.
2Measurement precision
If a cleavable linker is used to connect the protein of interest to the fluorescent reporter, then stoichiometric ratio is achieved, but the time delay between translation and fluorescence detection increases
Solution Approach 1:
The large fragment of the fluorescent protein (GFP1-10) is pre-expressed and pre-folded in the cell before the protein of interest is translated. This preliminary preparation means that when the small fragment (GFP11) is produced and the linker is cleaved, the association and fluorescence generation occur rapidly without waiting for the majority of the folding process. The cleavable linker still ensures stoichiometric quantification, but the detection delay is minimized to seconds.
3Loss of time
If the small fragment of split fluorescent protein is directly co-translated with the protein of interest without a cleavable linker, then folding time is reduced, but translation problems and improper folding of the small fragment occur
Solution Approach 1:
A cleavable linker (such as PQR or PTR linker) is introduced as an intermediary between the small fluorescent fragment (GFP11) and the protein of interest. During translation, this linker ensures proper co-translational folding and reliable expression of the small fragment. After translation is complete, the linker is proteolyzed by cellular proteases, releasing the small fragment to rapidly associate with the large fragment and form the functional fluorescent reporter. This intermediary approach resolves both the reliability of translation and the speed of fluorescence generation.
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
This approach enables instantaneous detection of protein translation with high spatial and temporal resolution, allowing for precise localization and quantification of protein synthesis events in subcellular compartments, such as the endoplasmic reticulum or neuronal dendrites.
Implementation Method 1
a cleavable protein linker (a small peptide), linking the protein of interest not to the entire fluorescent protein, but to a small fragment (i.e. an active portion) of a split fluorescent protein
Implementation Method 2
once the cleavable protein linker is cleaved, the small fragment of the split fluorescent protein associates with the larger portion, thereby constituting the fluorescent protein, and causing fluorescence
Data Source
AI summary
A method of quantifying expression of a protein of interest with high temporal resolution; it includes providing a cell expressing a large fragment of a split fluorescent protein; transfecting the cell with a vector comprising a nucleic acid molecule comprising a first nucleic acid sequence encoding the protein of interest; a second nucleic acid sequence encoding the small fragment of the split fluorescent protein; and a third nucleic acid sequence encoding a linker protein that is cleaved during translation; quantifying expression of the protein of interest by detecting fluorescence resulting from a combining of the small fragment of the split fluorescent protein and the large fragment of the split fluorescent protein, wherein the linker protein is cleaved during the translation resulting in a stoichiometric ratio of the small fragment of the split fluorescent protein and the protein of interest.