Engineered Promiscuous Biotin Ligases for Rapid Proximity Labeling
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Solution Overview
Problem
BioID's slow kinetics and low catalytic activity limit its application in studying dynamic processes and restrict its use in certain contexts, such as the ER lumen of mammalian cells and in organisms like yeast, worms, and flies, due to the need for prolonged biotin labeling and toxicity concerns.
Innovation Solution
Engineered promiscuous biotin ligases with specific amino acid substitutions and N-terminal deletions, such as TurboID and miniTurbo, which enhance biotinylation efficiency, allowing for rapid protein labeling in as little as 10 minutes with minimal toxicity, enabling the study of dynamic processes and expanding PL to new settings and organisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If BioID is used for proximity labeling, then the labeling protocol is simple and non-toxic conditions are maintained, but the kinetics are slow requiring 18-24 hours labeling time
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues in the BirA biotin ligase structure (e.g., R118G, R118S, E313K, E313R substitutions) to enhance catalytic activity. These point mutations modify the enzyme's kinetic parameters, increasing turnover rate while preserving the overall labeling protocol simplicity and non-toxic biotin-based chemistry.
2Object-affected harmful factors
If BioID is used for proximity labeling, then non-toxic labeling conditions are maintained, but catalytic activity is low making it difficult to apply in certain contexts
Solution Approach 1:
The patent improves catalytic activity through targeted amino acid substitutions (R118G, R118S, E313K, E313R) that enhance the enzyme's turnover rate. These mutations increase reliability of biotinylation in challenging contexts (ER lumen, yeast, worms, flies) while preserving the non-toxic biotin-based labeling chemistry, thus maintaining low harmful factors.
3Productivity
If APEX2 is used for proximity labeling, then labeling speed is fast within 1 minute, but H2O2 is toxic to cells and difficult to deliver without severe tissue damage
Solution Approach 1:
The patent converts the harmful peroxide-based chemistry of APEX2 into a beneficial non-toxic alternative by using engineered biotin ligases that catalyze biotin transfer using only biotin and ATP as substrates. This eliminates H2O2 toxicity while achieving rapid biotinylation kinetics through mutations like R118G and E313K.
Solution Approach 2:
The patent substitutes the peroxide-dependent peroxidase mechanism of APEX2 with an ATP-dependent biotin ligase mechanism. The engineered BirA variants use biotin-AMP intermediate chemistry instead of H2O2 oxidation, replacing a toxic mechanical system with a benign biochemical system while maintaining fast kinetics.
4Ease of operation
If BioID is used for proximity labeling, then simplicity of protocol is maintained, but labeling time is prolonged to 18-24 hours or much longer
Solution Approach 1:
The patent reduces labeling duration from 18-24 hours to under 2 hours by introducing catalytically enhanced mutations (R118G, R118S, E313K, E313R) that increase the turnover rate of biotin transfer. The protocol remains simple and uses only biotin addition, but the enhanced kinetics dramatically reduce the time required to accumulate sufficient biotinylated material.
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 modified biotin ligases achieve faster and more efficient proximity labeling, overcoming the limitations of BioID by enabling rapid biotinylation of proteins in various cellular contexts without causing significant toxicity, thus expanding the utility of proximity labeling techniques.
Implementation Method 1
a promiscuous labeling enzyme is targeted by genetic fusion to a specific protein or subcellular region. Addition of a small molecule substrate, such as biotin, initiates covalent tagging of endogenous proteins
Data Source
AI summary
Engineered promiscuous biotin ligases and methods of using them in proximity labeling are described. In particular, the invention provides novel biotin ligase variants having increased promiscuous biotinylation activity capable of proximity labeling of proteins in live cells in as little as 10 minutes.