GPCR Active State Stabilization via Nanobody Binding
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Solution Overview
Problem
Current methods fail to effectively stabilize and crystallize the active conformational state of G protein-coupled receptors (GPCRs), which is crucial for understanding signaling mechanisms and structure-based drug discovery, due to their biochemical instability and conformational heterogeneity.
Innovation Solution
A complex comprising a protein binding domain, specifically a nanobody sequence, that binds to an intracellular conformational epitope of a GPCR, stabilizing its active state and enhancing the receptor's affinity for agonists, allowing for high-resolution structural analysis and crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to crystallize GPCRs, then inactive state structures can be obtained, but active state structures cannot be obtained due to biochemical instability and conformational heterogeneity
Solution Approach 1:
The patent uses an engineered T4 lysozyme domain as an intermediary component that binds to the intracellular side of the GPCR and stabilizes the active conformational state. This intermediary protein acts as a molecular scaffold that maintains the receptor in its active state, enabling crystallization without requiring the presence of G proteins or other complex signaling components.
Solution Approach 2:
The patent employs site-directed mutagenesis to introduce specific amino acid substitutions in the T4 lysozyme domain and GPCR interface regions. These parameter changes at the molecular level optimize the interaction between the stabilizing domain and the receptor, thereby stabilizing the active conformational state and enabling crystal formation.
2Productivity
If GPCRs are expressed in recombinant systems without stabilization, then protein production is achieved, but high-resolution crystal structures cannot be obtained due to biochemical instability
Solution Approach 1:
The patent divides the GPCR system into separate functional components: the signaling-competent GPCR and the stabilization function provided by the engineered T4 lysozyme domain. This segmentation allows the receptor to be produced in recombinant systems for high productivity while the stabilizing domain ensures biochemical stability and crystallizability without interfering with natural signaling pathways.
Solution Approach 2:
The patent creates a composite protein complex consisting of the GPCR fused or associated with the engineered T4 lysozyme domain. This composite structure combines the signaling functionality of the native receptor with the stabilizing properties of the engineered domain, enabling both high-resolution structural analysis and maintenance of biochemical stability.
3Stability of the object's composition
If inverse agonists are used to stabilize GPCRs, then inactive state structures can be obtained, but active state structures remain inaccessible
Solution Approach 1:
Instead of using inverse agonists to stabilize the inactive state (conventional approach), the patent inverts the strategy by using an engineered stabilizing domain to actively promote and lock the active conformational state. This inversion enables access to active state structures that are otherwise inaccessible through conventional pharmacological stabilization methods.
Data Source
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AI summary
The present invention relates to the field of GPCR structure biology and signaling. In particular, the present invention relates to protein binding domains directed against or capable of specifically binding to a functional conformational state of a G-protein coupled receptor (GPCR). More specifically, the present invention provides protein binding domains that are capable of increasing the stability of a functional conformational state of a GPCR, in particular increasing the stability of a GPCR in its active conformational state. The protein binding domains of the present invention can be used as a tool for the structural and functional characterization of G-protein coupled receptors bound to various natural and synthetic ligands, as well as for screening and drug discovery efforts targeting GPCRs. Moreover, the invention also encompasses the diagnostic, prognostic and therapeutic usefulness of these protein binding domains for GPCR-related diseases.