A miniaturized MR1 metabolite display system with native-like protein features

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Major histocompatibility complex class I-related protein 1 (MR1) is crucial for immune surveillance by presenting metabolite antigens to T cells.
• Native MR1 protein instability hinders biochemical and structural studies, limiting understanding of its function.

Purpose of the Study:

• To develop a stabilized, minimal MR1 system (SMART-MR1) for enhanced biochemical and structural analysis.
• To facilitate studies on MR1-ligand binding and T cell receptor (TCR) recognition.

Main Methods:

• Engineered SMART-MR1 by fusing the MR1 α1/α2 domains to a stabilizing helical domain, replacing α3 and β2m.
• Utilized recombinant production, solution NMR, fluorescence polarization, isothermal titration calorimetry, and cryo-electron microscopy (cryo-EM).

Main Results:

• SMART-MR1 was efficiently produced and retained binding to diverse MR1 ligands.
• The system enabled NMR and fluorescence polarization-based ligand screening.
• SMART-MR1 demonstrated native-like binding to MAIT-derived TCRs and preserved MR1-ligand-TCR complex structure.

Conclusions:

• SMART-MR1 provides a minimal, stable, and native-like system for studying MR1.
• This platform expands experimental capabilities for MR1 research and therapeutic target discovery.