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M R Rosner

Publications and source records attributed to M R Rosner.

95 records · Page 6Linked to original sources
PubMed1980

Differences in glycosylation patterns of closely related murine leukemia viruses.

The nature of the carbohydrate chains in the major envelope glycoprotein of murine leukemia virus, gp70, and its cellular precursor has been investigated. A difference in the oligosaccharide composition of gp70 from an ecotropic murine leukemia virus (Akv) and three recombinant dual-tropic viruses [mink cell focus-inducing viruses (MCFs)] derived from Akv was demonstrated. Glycosidase digestion and gel filtration were utilized to identify the two classes of N-asparagine-linked oligosaccharides, high-mannose and complex. The gp70 of the ecotropic virus contained only N-linked oligosaccharides of the complex type. In contrast, the gp70s of the dual-tropic viruses contained both high-mannose and complex oligosaccharides. Analysis of gp70 glycopeptides from an MCF-related xenotropic virus showed an elution profile similar, but not identical, to profiles of the MCFs. The gp70 precursors isolated from cells infected with Akv or MCF virus contained N-linked oligosaccharides that were exclusively of the high-mannose type. Comparison of the high-mannose oligosaccharides of the MCF gp70 precursors with those of the corresponding gp70s indicated that very little further processing of the high-mannose residues in the gp70s had occurred. The presence of the high-mannose oligosaccharides in the envelope glycoprotein of the dual-tropic viruses results from altered carbohydrate processing. The conservation of this altered carbohydrate pattern in a number of hosts and under various conditions of growth suggests that the viral protein structure is the primary factor in determining the different mode of glycosylation of the MCF gp70s. Thus, these viral glycoproteins provide an important model system for studying the relationship between protein structure and patterns of glycosylation.

Animals↗
PubMed1980

Relationship of GIX antigen expression to the glycosylation of murine leukemia virus glycoprotein.

The GIX antigen, which is expressed on the surface of thymocytes of certain mouse strains, is an antigenic determinant of the major envelope glycoprotein of murine leukemia virus (gp70). Although GIX is expressed in some mouse strains that appear to be free of virus, the antigen can also be induced in GIX- mice by infection with particular murine leukemia viruses (termed GIX+). We have investigated the envelope gene products from two closely related viruses that differ in their GIX phenotype. Analysis of the envelope protein precursors by polyacrylamide gel electrophoresis and endoglycosidase treatment indicated that the GIX+ viral protein contained six oligosaccharide chains, whereas the GIX- viral protein contained seven. The observed differences in gel electrophoretic mobilities and glycopeptide profiles of the respective glycosylated envelope gene cleavage products (gp70) may be accounted for by the presence of an additional oligosaccharide chain on the gp70 of the GIX- virus. No differences between the apparent molecular weights of the nonglycosylated product of the envelope gene (p15E) were detected. These results suggest that the GIX- virus codes for an extra glycosylation site relative to the GIX+ virus, and this oligosaccharide chain is present both on the envelope gene precursor (Prenv) and on the major cleavage product (gp70). Recent nucleotide sequence analyses of selected RNase T1 oligonucleotides from the genomes of viruses that differ in GIX phenotype have similarly suggested that there may be a correlation between the GIX- phenotype and an extra glycosylation site [Donis-Keller, H., Rommelaere, J., Ellis, R. W. & Hopkins, N. (1980) Proc. Natl. Acad. Sci. USA 77, 1642-1645]. The results of these two different approaches raise the possibility that the presence of an additional oligosaccharide chain on gp70 may, either directly or indirectly, mask the expression of the GIX antigen on the surfaces of thymocytes and virus-infected cells.

Animals↗
PubMed1979

Structure of the lipopolysaccharide from an Escherichia coli heptose-less mutant. I. Chemical degradations and identification of products.

The structure of lipopolysaccharide from a heptose-less mutant of Escherichia coli K-12 has been investigated. Lipopolysaccharide isolated from 32P-labeled cells was treated with mild alkali to yield two separable components: [OH-LPS]-I (approximately 70%) and [OH-LPS]-II (approximately 30%). Mild acidic treatment of [OH-LPS]-I gave mainly a product which was identified as (4-O-phosphoryl-N-beta-hydroxymyristyl-D-glucosaminyl)-beta(1 leads to 6)-N-beta-hydroxymyristyl-D-glucosamine 1-phosphate (Compound I). Further acidic hydrolysis of both [OH-LPS]-I and [OH-LPS]-II yielded as the main product (4-O-phosphoryl-N-beta-hydroxymyristyl-D-glucosaminyl)-beta(1 leads to 6)-N-beta-hydroxymyristyl-D-glucosamine (Compound II). The structures of the above products were deduced by a combination of compositional analyses, sensitivity to phosphomonoesterase, rates of hydrolysis of the phosphate groups and alkali-catalyzed beta elimination of the phosphate residues following appropriate oxidation of hydroxyl groups. These studies together with work reported in the accompanying papers have led to the identification of two species of lipopolysaccharide in the E. coli strain both of which contain a single glucosamine dissacharide unit but differ in having monosubstituted phosphate or pyrophosphate groups at the glycosidic position. Each species of lipopolysaccharide also appeared to be heterogeneous with respect to the number of esterified fatty acyl groups.

Alkaline Phosphatase↗
PubMed1979

The structure of lipopolysaccharide from an Escherichia coli heptose-less mutant. III. Two fatty acyl amidases from Dictyostelium discoideum and their action on lipopolysaccharide derivatives.

Two fatty acyl amidases have been partially purified from the slime mold, Dictyostelium discoideum. Their action on lipopolysaccharide derivatives, especially Compound I, has been studied. Amidase I removes specifically the beta-hydroxymyristyl group, which is present on the amino group adjacent to the C-1 phosphate. The product, Compound V, is then a substrate for Amidase II, which removes the remaining beta-hydroxymyristyl group from the amino group in the distal glucosamine ring to give Compound VI. Compound I itself is resistant to Amidase II. Thus, the two enzymes show a high degree of structural specificity. The structure of lipopolysaccharide from the E. coli K-12 mutant is concluded in the light of studies reported in this and the accompanying papers, and this structure is discussed in relation to other bacterial lipopolysaccharides.

Amidohydrolases↗