Ritva Niemelä

Learn More
During fertilization in mice, free-swimming sperm bind to mZP3, an 83-kDa glycoprotein present in the egg extracellular coat, the zona pellucida [Wassarman, P. M. (1990) Development 108, 1-17]. Mouse sperm recognize and bind to a specific class of serine/threonine-linked (O-linked) oligosaccharides present on mZP3. After binding to mZP3, sperm undergo a(More)
We show here that colon-carcinoma cell lines adhere to E-selectin via sialyl Lewis x and sialyl Lewis a (s(Lex) and s(Lea)) oligosaccharides and that this adhesion can be enhanced by TNF stimulation. To study in greater detail this endothelial binding, we analysed the mRNA expression and function of the enzymes participating in the generation of s(Lex) and(More)
The P-selectin counterreceptor PSGL-1 is covalently modified by mono alpha2,3-sialylated, multiply alpha1,3-fucosylated polylactosamines. These glycans are required for the adhesive interactions that allow this adhesion receptor-counterreceptor pair to facilitate leukocyte extravasation. To begin to understand the biosynthesis of these glycans, we have(More)
Affinity chromatography of unreduced oligosaccharides on a small column of immobilized wheat germ agglutinin (WGA) revealed high-binding affinities for several radiolabeled molecules containing at the reducing end either beta-D-GlcpNAc-(1----6)-D-Gal, beta-D-GlcpNAc-(1----6)-beta- D-Galp-(1----4)-D-GlcNAc, beta-D-GlcpNAc-(1----6)-beta-D-Galp-(1----4)DGlc,(More)
Sialyl Lewis x (sLex) oligosaccharides have been shown to be present in counterreceptors for L-selectin. We and others have previously shown that high endothelial cells in lymph nodes and at sites of inflammation express sLex. Here we show that also cultured human umbilical vein endothelial cells (HUVEC) express sLex on their cell surface. This(More)
The GalNAcbeta1-4GlcNAc determinant (LdN) occurs in some human and bovine glycoconjugates and also in lower vertebrates and invertebrates. It has been found in unsubstituted as well as terminally substituted forms at the distal end of conjugated glycans, but it has not been reported previously at truly internal positions of polylactosamine chains. Here, we(More)
Radiolabelled lacto-N-neohexaose was fucosylated with partially purified alpha (1,3)fucosyltransferase(s) from human milk. Structural analysis of the monofucosylated products obtained at an early stage of the reaction revealed that both distal branches of the acceptor had reacted equally well, generating Lewis x determinants, while the reducing end glucose(More)
A partially purified preparation of alpha 1,3-fucosyltransferase(s) from human milk was used to [14C]fucosylate oligosaccharides containing Gal beta 1-4GlcNAc units. Substitution of N-acetyllactosamine at position 3' with a beta-linked N-acetyl-glucosamine enhanced the reactivity of the acceptor, whereas similar substitution at position 6' was inhibitory.(More)
Human alpha3-fucosyltransferases (Fuc-Ts) are known to convert N-acetyllactosamine to Galbeta1-4(Fucalpha1-3)GlcNAc (Lewis x antigen); some of them transfer fucose also to GalNAcbeta1-4GlcNAc, generating GalNAcbeta1-4(Fucalpha1-3)GlcNAc determinants. Here, we report that recombinant forms of Fuc-TV and Fuc-TVI as well as Fuc-Ts of human milk converted(More)
Proposing to study the molecular mechanisms of mouse gamete adhesion with the aid of high affinity adhesion inhibitors of saccharide nature, we report here the enzymatic synthesis of a bivalent oligosaccharide Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3(Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-6)Gal beta(More)