Related Experiment Videos
Energy transfer between two peptides bound to one MHC class II molecule
R Tampé1, B R Clark, H M McConnell
1Stauffer Laboratory for Physical Chemistry, Stanford University, CA 94305.
Science (New York, N.Y.)
|October 4, 1991
Summary
Researchers studied how ovalbumin peptides bind to MHC class II molecules. Energy transfer experiments revealed distinct binding site structures in "floppy" versus "compact" MHC class II alpha beta heterodimers.
Area of Science:
- Immunology
- Biochemistry
- Molecular Biology
Background:
- Major histocompatibility complex (MHC) class II molecules present peptide antigens to T helper cells.
- Understanding the structural dynamics of peptide-MHC class II interactions is crucial for immune response modulation.
Purpose of the Study:
- To investigate the structural differences in peptide binding sites of MHC class II molecules.
- To characterize the conformation of ovalbumin peptide (Ova(323-339)) within different MHC class II complexes.
Main Methods:
- Fluorescent labeling of Ova(323-339) with fluorescein (FOva) and Texas Red (AcOva-KTR).
- Electrophoretic separation of MHC class II-peptide complexes on polyacrylamide gels.
- Fluorescence spectroscopy to detect Förster Resonance Energy Transfer (FRET) between labels.
Main Results:
- FRET was observed in the "floppy" alpha beta heterodimer band, indicating proximity of the N- and C-termini of the labeled peptide.
- FRET was absent in the "compact" alpha beta heterodimer band.
- Energy transfer was detected between truncated peptide fragments in both compact and floppy forms, suggesting distinct binding site organizations.
Conclusions:
- The "floppy" MHC class II alpha beta heterodimer likely possesses two distinct peptide binding regions, possibly arising from a conformational split of a larger site.
- "Compact" and "floppy" conformations of MHC class II molecules exhibit different peptide binding site architectures.