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M Sumper

Publications and source records attributed to M Sumper.

At least 55 records · Page 3Linked to original sources
PubMed1987

The sexual inducer of Volvox carteri: purification, chemical characterization and identification of its gene.

The sexual inducer of Volvox carteri f. nagariensis is a glycoprotein and one of the most potent biological effector molecules known. It is synthesized by sperm cells and converts asexually growing males and females to the sexual pathway. Until now, large-scale production of the inducer was made impossible by an inherent biological ;switch' mechanism, the spontaneous self-induction of asexually growing males. Here we describe a method overcoming this problem for the first time. Large-scale production and purification allowed a detailed chemical characterization of the inducer with respect to partial amino acid sequences and sugar composition. Chemically synthesized oligodeoxynucleotides corresponding to derived amino acid sequences were used to screen a genomic gene bank of V. carteri HK 10. A positive clone (Ind-28) was shown to encode the inducer gene by subcloning and sequencing.

Journal Article↗
PubMed1986

A novel glycosphingolipid that may participate in embryo inversion in Volvox carteri.

Mouse monoclonal antibody 4-I-244 detects a developmentally regulated antigen in embryos of Volvox carteri and inhibits specifically the morphogenetic process of inversion (the process by which the embryo turns inside out). Antigen 4-I-244 was chemically characterized as a complex phytosphingolipid containing the neutral sugars xylose, galactose, and glucose as well as inositol and phosphate.

Antibodies, Monoclonal↗
PubMed1985

Halobacterial flagellins are sulfated glycoproteins.

The cell-surface glycoprotein of Halobacteria contains oligosaccharides of the type Glc4----1GlcA4----1GlcA4----1GlcA (where GlcA indicates glucuronic acid) with a sulfate group attached to each of the GlcA residues. We report here that in addition to this cell-surface glycoprotein, the halobacterial flagellar proteins (recently described by Alam, M., and Oesterhelt, D. (1984) J. Mol. Biol. 176, 459-475) also contain the same type of sulfated oligosaccharides. These flagellins have the following features. All of the individual flagellar proteins contain identical sulfated saccharide moieties linked to the amido nitrogen of Asn through a Glc residue (the novel type of N-glycosidic linkage that has been found in the cell-surface glycoprotein from Halobacteria (Wieland, F., Heitzer, R., and Schaefer, W. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 5470-5474)). The amino acid sequence of one carbohydrate-binding region is Gln-Ala-Ala-Gly-Ala-Asp-Asn-Jle-Asn-Leu-Thr-Lys. This surrounding sequence CHO is consistent with the general formula Asn-X-Thr(Ser), common to all N-linked glycopeptides determined so far. Biosynthesis of flagellar glycoconjugates involved sulfated oligosaccharides linked to dolichol monophosphate. The individual glycoproteins making up the flagella are structurally closely related to one another.

Amino Acid Sequence↗
PubMed1985

Transient methylation of dolichyl oligosaccharides is an obligatory step in halobacterial sulfated glycoprotein biosynthesis.

Biosynthesis of sulfated saccharides that are linked to asparagine residues in the cell surface glycoprotein of Halobacterium halobium via a glucose residue involves sulfated dolichyl-monophosphoryl oligosaccharide intermediates (Lechner, J., Wieland, F., and Sumper, M. (1985) J. Biol. Chem. 260, 860-866). During isolation and characterization of these lipid oligosaccharides we detected a group of related compounds containing additional unidentified sugar residues. Here we report that: 1) the unknown sugar residues were 3-O-methylglucose, linked peripherally to the lipid-saccharide intermediates; 2) the 3-O-methylglucose residues in the oligosaccharides occur only at the lipid-linked level but are absent at the protein-linked level; 3) cell surface glycoprotein biosynthesis in Halobacteria in vivo is drastically depressed when S-adenosylmethionine-dependent methylation is inhibited, indicating that methylation is an obligatory step during glycoprotein synthesis. We propose a mechanism for the transport of lipid oligosaccharides through the cell membrane, involving an intermediate stage in which the saccharide moieties are transiently modified with 3-O-methylglucose.

3-O-Methylglucose↗
PubMed1985

Biosynthesis of sulfated saccharides N-glycosidically linked to the protein via glucose. Purification and identification of sulfated dolichyl monophosphoryl tetrasaccharides from halobacteria.

A novel type of N-glycosidic linkage, asparaginyl glucose, occurs in the cell surface glycoprotein of halobacteria (Wieland, F., Heitzer, R., and Schaefer, W. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 5470-5474). Sulfated oligosaccharides containing glucuronic acids are attached to the polypeptide chain via this linkage. Here we describe the isolation and chemical characterization of lipid-linked precursors of these saccharides, and these have the following new features. Rather than the bacterial undecaprenol, a C60-dolichol is the carrier lipid. The oligosaccharide is bound to this lipid via a monophosphate, rather than a pyrophosphate bridge. Sulfation of the saccharides is completed while they are linked to lipid and does not occur after transfer of the saccharides to protein.

Asparagine↗
PubMed1984

Development-dependent modification of the extracellular matrix by a sulphated glycoprotein in Volvox carteri.

We report the chemical characterization of the highly sulphated glycoprotein SSG 185 from Volvox carteri. SSG 185 is a hydroxyproline-containing, extracellular glycoprotein. The sulphate residues are clustered within the parent saccharide structure of SSG 185, since on mercaptolysis all the sulphate residues are recovered in a small saccharide fragment containing mannose, arabinose and sulphate (in a molar ratio of 112). SSG 185 is a short-lived molecule, serving as a precursor for a high mol. wt. component of the extracellular matrix. Synthesis of SSG 185 is developmentally controlled. Different SSG 185 variants, with unknown modifications in the sulphated saccharide fragment, are synthesized at different developmental stages or under the influence of the sexual inducer. These modifications remain conserved in the aggregated state of SSG 185, indicating the development-dependent modification of the extracellular matrix.

Journal Article↗
PubMed1981

Sulfation of a cell surface glycoprotein correlates with the developmental program during embryogenesis of Volvox carteri.

A sulfated cell surface glycoprotein with an apparent molecular weight of 185,000 is synthesized in the multicellular organism Volvox only during the limited period of embryogenesis. The lifetime of sulfate residues on this glycoprotein is very short (half-life about 20 min). Production of this sulfated glycoprotein sharply decreases to a minimum shortly before the onset of the differentiating cell cleavage--e.g., in asexual development, before the 32-cell embryo divides. It is demonstrated that the sulfated glycoprotein behaves in many respects as would the hypothetical cell surface component postulated by a recently published model [Sumper, M. (1979) FEBS Lett. 107, 241-246], which proposes an explanation for the cell-counting mechanism and the spatial control of differentiation that is operative in Volvox embryogenesis.

Cell Adhesion↗
PubMed1978

Studies on the biosynthesis of bacterio-opsin. Demonstration of the existence of protein species structurally related to bacterio-opsin.

1. The kinetics of processing newly synthesized bacterio-opsin from the non-crystalline state within the brown membrane to the crystalline state within the purple membrane was followed by pulse-chase experiments. 2. Biosynthesis of bacterio-opsin was found to be highly resistant to RNA-synthesis inhibitors like rifampicin and ethidium bromide. In the presence of ethidium bromide, only five protein species continue to be synthesized in halobacteria, one of them being bacterio-opsin. 3. In spheroplasts, synthesis of bacterio-opsin is found to be selectively disturbed. The purple membrane isolated from spheroplasts contains new, additional protein species with apparent molecular weights of 19 000, 23 000 and 29 000. These proteins share common amino acid sequences with bacterio-opsin. 4. In the halobacterial cell membrane, two membrane proteins with apparent molecular weights of 30 000 and 36 000 were detected which are structurally related to bacterio-opsin. 5. Bacterio-opsin as well as the 30 000 Mr and 36 000-Mr proteins contain covalently bound sulphate.

Amino Acid Sequence↗