Bacterial Phytochrome Optogenetic System NIR Control
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Solution Overview
Problem
Current optogenetic systems face challenges in controlling protein-protein interactions and gene expression in living mammals due to limitations in light penetration, chromophore availability, and spectral compatibility, particularly in the near-infrared range.
Innovation Solution
Development of a light-inducible optogenetic system based on the interaction between Rhodopseudomonas palustris BphP1 and PpsR2, utilizing biliverdin as a chromophore, which is abundant in mammalian cells, and sensitive to near-infrared light, allowing for reversible protein binding and gene expression control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If blue light-sensitive photoreceptors (LOV, BLUF, cryptochrome) are used for optogenetic control, then protein-protein interactions can be activated with high precision, but light penetration depth in mammalian tissues is limited
Solution Approach 1:
The patent changes the spectral parameter of the photoreceptor from blue-light sensitive to near-infrared light sensitive by using bacterial phytochrome with biliverdin chromophore. This allows the system to operate in the 650-900 nm tissue transparency window while maintaining optogenetic control precision through light-induced conformational changes and protein-protein interactions.
2Illumination intensity
If plant phytochrome based systems are used for near-infrared optogenetics, then light penetration depth is improved, but exogenous chromophore supply is required which complicates the system
Solution Approach 1:
The patent employs bacterial phytochrome that utilizes biliverdin, a chromophore that is naturally abundant in mammalian cells as a heme degradation product. This eliminates the need for exogenous chromophore supply required by plant phytochrome systems, as the bacterial phytochrome can directly utilize endogenous biliverdin for near-infrared light sensing and optogenetic control.
3Illumination intensity
If bacterial phytochrome with biliverdin chromophore is used, then near-infrared light sensitivity is achieved with improved tissue penetration, but protein dimerization control efficiency may be reduced
Solution Approach 1:
The patent utilizes the reversible photoconversion dynamics of bacterial phytochrome between Pr and Pfr states to dynamically control protein-protein interactions. The system can be activated by near-infrared light inducing Pfr formation, and deactivated by red light or thermal relaxation returning to Pr state, providing temporal control while maintaining high activation rates through optimized fusion protein design.
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 system enables precise and reversible control of protein interactions and gene expression with high sensitivity to near-infrared light, achieving significant protein translocation and gene activation with minimal interference with cellular metabolism, and improved tissue penetration compared to existing systems.
Implementation Method 1
Within a chromophore-binding pocket BV can adopt two conformational states, termed Pr and Pfr and absorbing far-red and NIR light, respectively. Isomerization of BV chromophore between Pr and Pfr states causes conformational changes in the protein backbone
Implementation Method 2
a range of wavelengths where light exhibits maximum depth of tissue penetration due to low light-scattering and minimal absorbance of melanin, hemoglobin and water lies between 650 and 900 nm, and is called a near infra-red (NIR) tissue transparency window
Data Source
AI summary
A novel optogenetic system, including constructs and methods, is provided based on the interaction of Rhodopseudomonas palustris BphP1 and Rhodopseudomonas palustris PpsR2 or a non-dimerizing variant thereof.