Murine MHC class Ib gene, H2-M2, encodes a conserved surface-expressed glycoprotein.
We have determined the genomic sequence of H2-M2 in seven haplotypes from nine inbred strains of mice and in five wild-derived haplotypes. Except for the spretus haplotype sp1 with a premature stop codon, we found only limited polymorphism. Four of the five amino acid substitutions in the alpha-helices are at positions that would point out from the antigen-binding groove, indicating that the polymorphism might influence receptor recognition rather than antigen binding. The rat homologue, RT1.M2(lv1), has 89% identity to H2-M2 at the nucleotide level and 91% at the amino acid level, and it also encodes an intact MHC class I glycoprotein. Chimeric proteins with alpha(1)alpha(2) or alpha(3)-transmembrane domains encoded by H2-Q9 were detectable on the surface of transfectants with monoclonal antibodies against Qa2, and the full-length M2 protein, labeled by fusion with green fluorescent protein, was detectable with S19.8 monoclonal antibodies. The H2-M2 protein was thus expressed on the cell surface, even in TAP-deficient RMA-S cells at 37 degrees C, suggesting that it is TAP-independent. We conclude that H2-M2 is a conserved mouse class Ib gene that is translated to a surface-expressed MHC class I molecule with a function still to be elucidated.
Moore
Yuki F
YF
Howard Hughes Medical Institute and Center for Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9050, USA.
Lambracht-Washington
Doris
D
Tabaczewski
Piotr
P
Fischer Lindahl
Kirsten
K
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D005805:Genes, MHC Class I; D006367:HeLa Cells; D006649:Histocompatibility Antigens / Q000235:genetics; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D018076:DNA, Complementary; C416189:H2-M antigens; D006649:Histocompatibility Antigens; D000949:Histocompatibility Antigens Class II; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; C038353:histocompatibility antigens RT, rat