1. ST8SIA4-Dependent Polysialylation is Part of a Developmental Program Required for Germ Layer Formation from Human Pluripotent Stem Cells.

    Stem Cells 34(7):1742 (2016) PMID 27074314 PMCID PMC4931981

    Polysialic acid (PSA) is a carbohydrate polymer of repeating α-2,8 sialic acid residues that decorates multiple targets, including neural cell adhesion molecule (NCAM). PST and STX encode the two enzymes responsible for PSA modification of target proteins in mammalian cells, but despite widespre...
  2. Structural basis for regulation of human calcium-sensing receptor by magnesium ions and an unexpected tryptophan derivative co-agonist.

    Science advances 2(5):e1600241 (2016) PMID 27386547 PMCID PMC4928972

    Ca(2+)-sensing receptors (CaSRs) modulate calcium and magnesium homeostasis and many (patho)physiological processes by responding to extracellular stimuli, including divalent cations and amino acids. We report the first crystal structure of the extracellular domain (ECD) of human CaSR bound with...
  3. Mucin-type O-glycosylation is controlled by short- and long-range glycopeptide substrate recognition that varies among members of the polypeptide GalNAc transferase family.

    Glycobiology 26(4):360 (2016) PMID 26610890 PMCID PMC4767052

    A large family of UDP-GalNAc:polypeptide GalNAc transferases (ppGalNAc-Ts) initiates and defines sites of mucin-type Ser/Thr-O-GalNAc glycosylation. Family members have been classified into peptide- and glycopeptide-preferring subfamilies, although both families possess variable activities again...
  4. Selective Exo-Enzymatic Labeling Detects Increased Cell Surface Sialoglycoprotein Expression upon Megakaryocytic Differentiation.

    Journal of Biological Chemistry 291(8):3982 (2016) PMID 26733198 PMCID PMC4759176

    Selective exo-enzymatic labeling (or SEEL) uses recombinant glycosyltransferases and nucleotide-sugar analogues to allow efficient labeling of cell surface glycans. SEEL can circumvent many of the possible issues associated with metabolic labeling, including low incorporation of sugar precursors...
  5. The functional O-mannose glycan on α-dystroglycan contains a phospho-ribitol primed for matriglycan addition.

    eLife 5 (2016) PMID 27130732 PMCID PMC4924997

    Multiple glycosyltransferases are essential for the proper modification of alpha-dystroglycan, as mutations in the encoding genes cause congenital/limb-girdle muscular dystrophies. Here we elucidate further the structure of an O-mannose-initiated glycan on alpha-dystroglycan that is required to ...
  6. ERManI (Endoplasmic Reticulum Class I α-Mannosidase) Is Required for HIV-1 Envelope Glycoprotein Degradation via Endoplasmic Reticulum-associated Protein Degradation Pathway.

    Journal of Biological Chemistry 290(36):22184 (2015) PMID 26205822 PMCID PMC4571969

    Previously, we reported that the mitochondrial translocator protein (TSPO) induces HIV-1 envelope (Env) degradation via the endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway, but the mechanism was not clear. Here we investigated how the four ER-associated glycoside hydrola...
  7. Helicobacter pylori chronic infection and mucosal inflammation switches the human gastric glycosylation pathways.

    Biochimica et Biophysica Acta 1852(9):1928 (2015) PMID 26144047 PMCID PMC4638172

    Helicobacter pylori exploits host glycoconjugates to colonize the gastric niche. Infection can persist for decades promoting chronic inflammation, and in a subset of individuals lesions can silently progress to cancer. This study shows that H. pylori chronic infection and gastric tissue inflamma...
  8. A PEGylated photocleavable auxiliary mediates the sequential enzymatic glycosylation and native chemical ligation of peptides.

    Angewandte Chemie. International edition in Eng... 54(26):7711 (2015) PMID 25980981 PMCID PMC4524672

    Research aimed at understanding the specific role of glycosylation patterns in protein function would greatly benefit from additional approaches allowing direct access to homogeneous glycoproteins. Herein the development and application of an efficient approach for the synthesis of complex homog...
  9. High structural resolution hydroxyl radical protein footprinting reveals an extended Robo1-heparin binding interface.

    Journal of Biological Chemistry 290(17):10729 (2015) PMID 25752613 PMCID PMC4409239

    Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, ...
  10. High Yield Expression of Recombinant Human Proteins with the Transient Transfection of HEK293 Cells in Suspension.

    Journal of Visualized Experiments (106):e53568 (2015) PMID 26779721 PMCID PMC4780855

    The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and function. The rapid establishment and high recovery from transiently-transfected mammalian cell lines addresses this barrier and is an effective means...
  11. Direct determination of multiple ligand interactions with the extracellular domain of the calcium-sensing receptor.

    Journal of Biological Chemistry 289(48):33529 (2014) PMID 25305020 PMCID PMC4246106

    Numerous in vivo functional studies have indicated that the dimeric extracellular domain (ECD) of the CaSR plays a crucial role in regulating Ca(2+) homeostasis by sensing Ca(2+) and l-Phe. However, direct interaction of Ca(2+) and Phe with the ECD of the receptor and the resultant impact on its...
  12. Two Arabidopsis proteins synthesize acetylated xylan in vitro.

    Plant Journal 80(2):197 (2014) PMID 25141999 PMCID PMC4184958

    Xylan is the third most abundant glycopolymer on earth after cellulose and chitin. As a major component of wood, grain and forage, this natural biopolymer has far-reaching impacts on human life. This highly acetylated cell wall polysaccharide is a vital component of the plant cell wall, which fu...
  13. Changes in glycosaminoglycan structure on differentiation of human embryonic stem cells towards mesoderm and endoderm lineages.

    Biochimica et Biophysica Acta 1840(6):1993 (2014) PMID 24412195 PMCID PMC4004645

    Proteoglycans are found on the cell surface and in the extracellular matrix, and serve as prime sites for interaction with signaling molecules. Proteoglycans help regulate pathways that control stem cell fate, and therefore represent an excellent tool to manipulate these pathways. Despite their ...
  14. Probing the impact of GFP tagging on Robo1-heparin interaction.

    Glycoconjugate Journal 31(4):299 (2014) PMID 24748467 PMCID PMC4118743

    Green fluorescent proteins (GFPs) and their derivatives are widely used as markers to visualize cells, protein localizations in in vitro and in vivo studies. The use of GFP fusion protein for visualization is generally thought to have negligible effects on cellular function. However, a number of...
  15. Sparse labeling of proteins: structural characterization from long range constraints.

    PMID 24656078 PMCID PMC3964372

    Structural characterization of biologically important proteins faces many challenges associated with degradation of resolution as molecular size increases and loss of resolution improving tools such as perdeuteration when non-bacterial hosts must be used for expression. In these cases, sparse is...
  16. B4GAT1 is the priming enzyme for the LARGE-dependent functional glycosylation of α-dystroglycan.

    eLife 3 (2014) PMID 25279697 PMCID PMC4227051

    Recent studies demonstrated that mutations in B3GNT1, an enzyme proposed to be involved in poly-N-acetyllactosamine synthesis, were causal for congenital muscular dystrophy with hypoglycosylation of α-dystroglycan (secondary dystroglycanopathies). Since defects in the O-mannosylation protein gly...
  17. Heparan sulfate deficiency disrupts developmental angiogenesis and causes congenital diaphragmatic hernia.

    Journal of Clinical Investigation 124(1):209 (2014) PMID 24355925 PMCID PMC3871243

    Congenital diaphragmatic hernia (CDH) is a common birth malformation with a heterogeneous etiology. In this study, we report that ablation of the heparan sulfate biosynthetic enzyme NDST1 in murine endothelium (Ndst1ECKO mice) disrupted vascular development in the diaphragm, which led to hypoxia...
  18. Selective exo-enzymatic labeling of N-glycans on the surface of living cells by recombinant ST6Gal I.

    Angewandte Chemie. International edition in Eng... 52(49):13012 (2013) PMID 24129959 PMCID PMC3869382

    A game of tag: N-Glycans on the surface of living cells were selectively tagged by exogenously administering recombinant ST6Gal I sialyltransferase and azide-modified CMP-Neu5Ac. This modification was followed by a strain-promoted cycloaddition using a biotin-modified dibenzylcyclooctynol (red s...
  19. Enzymatic basis for N-glycan sialylation: structure of rat α2,6-sialyltransferase (ST6GAL1) reveals conserved and unique features for glycan sialylation.

    Journal of Biological Chemistry 288(48):34680 (2013) PMID 24155237 PMCID PMC3843080

    Glycan structures on glycoproteins and glycolipids play critical roles in biological recognition, targeting, and modulation of functions in animal systems. Many classes of glycan structures are capped with terminal sialic acid residues, which contribute to biological functions by either forming ...
  20. The 2013 Karl Meyer Award and Rosalind Kornfeld Award from the Society for Glycobiology.

    Glycobiology 23(11):1207 (2013) PMID 24127495