Structural Differences between the Mouse H-2D Products of the Mutant B10.D2.M504 (H-2da) and the Parental Nonmutant Strain B10.D2 (H-2d)

Abstract

Abstract The H-2K and H-2D glycoproteins from the mutant mouse strain B10.D2.M504 (H-2Kd,Dda) were compared with the H-2K and H-2D molecules from the parent nonmutant strain B10.D2 (H-2Kd,Dd). Whereas in every respect the K molecules of the mutant and nonmutant cells were identical, the Dda molecule from the mutant showed notable differences from the Dd molecule of the nonmutant parent. First, smaller amounts (ca. 25%) of the Dda glycoprotein appeared to be present in M504 cell extracts as compared to the amount of Dd glycoprotein present in nonmutant cell extracts. Second, a proportion of the Dda glycoprotein molecules showed an abnormal interaction with the lectin from lentil beans (LcH), suggesting an altered carbohydrate chain on some of the molecules. Third, comparative tryptic peptide analysis showed a significant degree of diversity between the mutant Dda molecule and the nonmutant Dd molecule. Thus, analysis of arginine-labeled peptides showed at least two peptides unique to H-2Dd and at least three peptides unique to H-2Dda. Analysis of lysine-labeled peptides showed at least three peptides unique to H-2Hd and greater than two peptides unique to the mutant H-2Dda. These data thus document that the Dda glycoprotein has an altered primary amino acid sequence as compared to the nonmutant Dd molecule. The finding of differences in greater than one-third of the total peptides recovered correlates with the strong serologic and histogenic reactivity between the cells of the M504 mutant and the cells of the B10.D2 parent. This peptide diversity is in contrast to the small degree of variation (ca. 10%) noted for the mutants of the H-2Kb locus (e.g., H-2Kba, H-2Kbd) which have only histogenic reactivity and essentially no serologic differences between mutant and nonmutant cells. The multiple structural differences noted between H-2Dd and H-2Dda suggest that a complex mutation has taken place.