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H2-M3, a full-service class Ib histocompatibility antigen
K F Lindahl1, D E Byers, V M Dabhi
1Howard Hughes Medical Institute, Departments of Microbiology and Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235-9050, USA.
Annual Review of Immunology
|January 1, 1997
Summary
Histocompatibility antigen H2-M3 uniquely binds N-formylated peptides from bacteria or mitochondria. Its crystal structure reveals a distinct binding groove, explaining its role in presenting self and foreign antigens.
Area of Science:
- Immunology
- Structural Biology
- Molecular Biology
Background:
- H2-M3 is a mouse MHC class Ib molecule.
- It uniquely binds N-formylated peptides from endogenous or foreign sources.
- MHC molecules present peptides to T cells, influencing immune responses.
Purpose of the Study:
- To elucidate the structural basis for H2-M3's N-formylated peptide binding preference.
- To understand how H2-M3 functions as a histocompatibility antigen.
Main Methods:
- X-ray crystallography to determine the H2-M3-peptide complex structure.
- Analysis of the peptide-binding groove and interactions.
Main Results:
- The crystal structure revealed a hydrophobic peptide-binding groove with an occluded A pocket.
- A novel hydrogen bonding network involving His9 anchors the formyl group.
- The P1 methionine side chain occupies the B pocket.
- H2-M3 presents endogenous peptides as minor histocompatibility antigens and bacterial antigens.
Conclusions:
- H2-M3's unique structure dictates its specific N-formylated peptide binding.
- This binding preference enables H2-M3 to act as a versatile histocompatibility antigen in immune surveillance and response.