Notable diversity in peptide composition of murine H-2K and H-2D alloantigens

Comparative tryptic peptide analysis was used to probe the structure of the TL products coded for by normally expressed TL alleles (Tlaa and TlaC haplotypes) and the structure of the TL product on ERLD, a TL+ leukemia occurring in a strain that does not normally express TL antigens (Tiab haplotype). In mice that have the Tid' haplotype, the peptide maps of TL glycoproteins from normal thymocytes and from TL+ leukemias were identical, a finding that is consistent with the indistinguishable serologically defined TL phenotype of these cells. Analysis of the Th product on ERLD leukemia cells (TL phenotype, TL.1,2,4) indicates a single TL glycoprotein species with the TL.4 determinant (restricted to leukemias of Tiab and Tiac haplotypes) coexisting on the same glycoprotein as the TL. 1 determinant (normally expressed by thymocytes of Tiaa haplotype). Comparison of the peptides of the TL product of ERLD and the products of the normally expressed Tid' and TLaC loci showed a high degree of structural similarity (i.e., 70-80%) ofshared peptides. In contrast, the products of the Tlaa, Tlab, and TlaC loci shared relatively few peptides with the products of the K, D, and L loci of the closely linked major histocompatibility complex (15-35%). The TL family, therefore, consists of alleles that are highly homologous. This contrasts with the marked diversity and polymorphism among the alleles of the K, D, and L loci.The TL system of cell surface antigens was discovered almost 20 years ago during studies of mouse leukemia (1). A number of unique features set TL apart from other surface antigenic systems (2). In certain strains of mice (designated TL+ strains), TL has the characteristics of a differentiation antigen, expression being limited to thymocytes and leukemia cells of thymic origin. In other strains (TL-strains), TL is not normally expressed on thymocytes, but can be detected on leukemia cells. The usual explanation given for these findings is that all strains of mice have the genetic information for TL but strains differ with regard to regulatory sequences controlling expression vs. nonexpression of TL on normal thymocytes. Leukemogenesis disrupts this regulatory control of TL in TL-strains, resulting in the expression ofnormally silent TL genes and the anomalous appearance of TL antigens on leukemia cells.Mendelian analysis ofTL expression in normal mice showed that the controlling locus (designated Tla) is closely linked to

Section: Methodsmentioning

confidence: 99%

“…These procedures were carried out as described (17), except that the elution buffer for the Bio-Gel A column contained 0.02 M dithiothreitol (A grade, Calbiochem) and the trypsin digestion buffer included 0.1 M ammonium bicarbonate, pH 8.55.…”

Section: Methodsmentioning

confidence: 99%

Structural comparisons of TL antigens derived from normal and leukemia cells of Tl+ and TL- strains and relationship to genetically linked H-2 major histocompatibility complex products.

Yokoyama¹,

Stockert²,

Old³

et al. 1981

“…In the a-chains, about 50% of peptides are shared; similar levels of sharing have been reported between products of other discrete loci in the major histocompatibility complex (13). It seems clear that the two molecules are structurally very similar and almost certainly represent products of duplicate structural genes (6,17).…”

Section: Discussionmentioning

confidence: 57%

“…Recovery of radioactivity, from time of mixing of radiolabeled proteins to application of sample to the column, was consistently 65-85%. The chromatogram was developed at 510C with a five-chamber linear gradient as described by Brown et al (13). Samples were dried at 80°C and assayed for radioactivity.…”

mentioning

confidence: 99%

Structural characterization of the murine fourth component of complement and sex-limited protein and their precursors: Evidence for two loci in the S region of the H-2 complex

Parker

Roos

Shreffler

1979

The S region of the murine major histocompatibility complex controls the expression of two related, serum substance-positive proteins; one (C4) has functional complement activity, whereas the other, the sex-limited protein (Slp), is hemolytically nonfunctional. The whether the Slp-positive and Slp-negative subclasses of Ss protein represent the products of two distinct but closely linked and highly homologous structural genes in the S region, or whether the gene controlling the Slp variant might act via modification of the product of the Ss structural gene.Major progress in characterization of the Ss protein was made when it was demonstrated that it is antigenically (3, 4), structurally (3, 4), and functionally (5) homologous to the fourth component of human complement (C4). These observations were extended by studies in this laboratory (6) and subsequently by others (7), showing that the molecular weights of the isolated a-, p3-, and y-chains of the Ss protein (approximately 100,000, 75,000, and 34,000, respectively) are very similar to those reported for humans (8) and guinea pigs (9) C4. Differences were demonstrated in the apparent molecular weights of both the a-and y-chains between the Slp-negative and Slp-positive subclasses of Ss (6, 7). It was therefore proposed (6) that the Slp-positive and Slp-negative Ss molecules have different primary structures and represent the products of two discrete genes.Roos et al. (6) found an intracellular molecule with an apparent molecular weight of 185,000 which reacted with anti-Ss antibody-a putative C4 precursor. In accord with an earlier finding by Hall and Colten (10), in which an apparent singlechain precursor for guinea pig C4 was synthesized in a cell-free translation system, these findings suggested that a single structural gene might determine all three subunits of the C4 molecule.Recent data have also shown functional differences between Slp-positive and Slp-negative Ss molecules. Ferreira et al. (7) showed that the action of complement component C1 on Slp-negative molecules resulted in the cleavage of a small fragment (presumably C4a) from the a-chain, whereas no effect of complement component C1 on Slp-positive molecules was noted. Furthermore, functional studies with a hemolytic assay employing C4-deficient guinea pig serum indicated that only the Slp-negative Ss molecules possess C4 activity (ref. 7; J. P. Atkinson and D. C. Shreffler, unpublished results).The goals of the present study were 2-fold. First, we sought to demonstrate conclusively a precursor-product relationship between the 185,000-dalton intracellular molecules and the processed Slp-positive and Slp-negative Ss molecules. To this end, a combination of kinetic pulse-chase studies and structural comparisons by tryptic peptide mapping has been performed which confirms the suggestion (6) that the putative precursors give rise to the processed extracellular molecules. Second, the structural differences between Slp-positive and Slp-negative Ss molecules were further examined. Evidence ...

“…These molecules are noncovalently associated with 12-microglobulin (8), a polypeptide homologous to the constant region domains of immunoglobulin molecules (9). Numerous peptide map differences between the K and D gene products suggest that the multiple serological differences have their basis in multiple amino-acid substitutions (10 Strategy. Spleens were removed from mice and the cells were cultured in vitro for [4][5][6] hr with groups of tritiated amino acids (i.e., either alanine, lysine, and valine or leucine, proline, and tyrosine) (19).…”

mentioning

confidence: 99%

Structure and evolution of transplantation antigens: partial amino-acid sequences of H-2K and H-2D alloantigens.

Silver¹,

Hood²

1976