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Identification of the rat maternally transmitted minor histocompatibility antigen
P K Bhuyan1, L L Young, K F Lindahl
1Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas 75235, USA.
Abstract:
The rat maternally transmitted Ag has been previously described as a minor histocompatibility Ag composed of a mitochondrially transmitted factor (MTF) and the RT1.Aa MHC class I molecule. We compared the DNA sequences of the 13 mitochondrial open reading frames from different rat strains and identified four coding polymorphisms that correlated with this MTF. We used synthetic 17-mer peptides spanning the polymorphisms to sensitize appropriate target cells in lymphocytotoxicity assays and found that the MTF is derived from an internal region of ATPase 6. A tridecameric derivative of the ATPase 6 17 mer (termed 13N3E) could sensitize RT1.Aa-expressing target cells at picomolar concentrations and, when present on such cells, could compete fully with the natural ligand in cold-target competition assays. Comparing the 13N3E peptide with the known peptide-binding requirements of RT1.Aa suggested two possible binding conformations, placing either an internal or a C-terminal arginine in the F pocket of the peptide-binding groove. Arguments favoring a "bulging" conformation, with N- and C-terminal residues bound into their conserved pockets, are discussed.
Insights
Researchers identified the rat maternally transmitted antigen (MTF) as a peptide from mitochondrial ATPase 6. This peptide binds to the RT1.Aa MHC class I molecule, influencing immune responses.
Area of Science:
- Immunology
- Mitochondrial Genetics
- Molecular Biology
Background:
- The rat maternally transmitted antigen (MTF) is a minor histocompatibility antigen.
- MTF is understood to be composed of a mitochondrially transmitted factor and the RT1.Aa MHC class I molecule.
Purpose of the Study:
- To identify the specific protein source of the MTF.
- To characterize the interaction between the MTF and the RT1.Aa molecule.
Main Methods:
- DNA sequencing of mitochondrial open reading frames in different rat strains.
- Peptide synthesis and lymphocytotoxicity assays.
- Analysis of peptide-MHC binding conformations.
Main Results:
- Four coding polymorphisms in mitochondrial genes correlated with MTF.
- The MTF was identified as a peptide derived from the ATPase 6 gene.
- A specific ATPase 6-derived peptide (13N3E) sensitized RT1.Aa-expressing cells at picomolar concentrations.
- Peptide-binding analysis suggested a 'bulging' conformation for RT1.Aa.
Conclusions:
- The MTF is a peptide originating from mitochondrial ATPase 6.
- This peptide interacts with the RT1.Aa MHC class I molecule.
- Understanding this interaction provides insights into minor histocompatibility antigen presentation and immune recognition.