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Thoma J, Grabherr R, Staudacher E. Determination, expression and characterization of an UDP-N-acetylglucosamine:α-1,3-D-mannoside β-1,2-N-acetylglucosaminyltransferase I (GnT-I) from the Pacific oyster, Crassostrea gigas. Glycoconj J 2024; 41:151-162. [PMID: 38557922 PMCID: PMC11065688 DOI: 10.1007/s10719-024-10148-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 02/13/2024] [Accepted: 03/18/2024] [Indexed: 04/04/2024]
Abstract
Molluscs are intermediate hosts for several parasites. The recognition processes, required to evade the host's immune response, depend on carbohydrates. Therefore, the investigation of mollusc glycosylation capacities is of high relevance to understand the interaction of parasites with their host. UDP-N-acetylglucosamine:α-1,3-D-mannoside β-1,2-N-acetylglucosaminyltransferase I (GnT-I) is the key enzyme for the biosynthesis of hybrid and complex type N-glycans catalysing the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to the α-1,3 Man antenna of Man5GlcNAc2. Thereby, the enzyme produces a suitable substrate for further enzymes, such as α-mannosidase II, GlcNAc-transferase II, galactosyltransferases or fucosyltransferases. The sequence of GnT- I from the Pacific oyster, Crassostrea gigas, was obtained by homology search using the corresponding human enzyme as the template. The obtained gene codes for a 445 amino acids long type II transmembrane glycoprotein and shared typical structural elements with enzymes from other species. The enzyme was expressed in insect cells and purified by immunoprecipitation using protein A/G-plus agarose beads linked to monoclonal His-tag antibodies. GnT-I activity was determined towards the substrates Man5-PA, MM-PA and GnM-PA. The enzyme displayed highest activity at pH 7.0 and 30 °C, using Man5-PA as the substrate. Divalent cations were indispensable for the enzyme, with highest activity at 40 mM Mn2+, while the addition of EDTA or Cu2+ abolished the activity completely. The activity was also reduced by the addition of UDP, UTP or galactose. In this study we present the identification, expression and biochemical characterization of the first molluscan UDP-N-acetylglucosamine:α-1,3-D-mannoside β-1,2-N-acetylglucosaminyltransferase I, GnT-I, from the Pacific oyster Crassostrea gigas.
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Affiliation(s)
- Julia Thoma
- Department of Chemistry (DCH), University of Natural Resources and Life Sciences, Vienna, Austria
| | - Reingard Grabherr
- Department of Biotechnology (DBT), University of Natural Resources and Life Sciences, Vienna, Austria
| | - Erika Staudacher
- Department of Chemistry (DCH), University of Natural Resources and Life Sciences, Vienna, Austria.
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Barbosa EA, Alves GSC, Coura MDMA, Silva HDLE, Rocha FSD, Nunes JB, Watanabe MDS, Andrade AC, Brand GD. A first look at the N- and O-glycosylation landscape in anuran skin secretions. Biochimie 2022; 197:19-37. [DOI: 10.1016/j.biochi.2022.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 01/08/2022] [Accepted: 01/17/2022] [Indexed: 11/26/2022]
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Voglmeir J, Laurent N, Flitsch SL, Oelgeschläger M, Wilson IBH. Biological and biochemical properties of two Xenopus laevis N-acetylgalactosaminyltransferases with contrasting roles in embryogenesis. Comp Biochem Physiol B Biochem Mol Biol 2015; 180:40-7. [PMID: 25447273 PMCID: PMC4291152 DOI: 10.1016/j.cbpb.2014.10.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 10/14/2014] [Accepted: 10/16/2014] [Indexed: 12/20/2022]
Abstract
The biosynthesis of mucin-type O-linked glycans in animals is initiated by members of the large family of polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts), which play important roles in embryogenesis, organogenesis, adult tissue homeostasis and carcinogenesis. Until now, the mammalian forms of these enzymes have been the best characterized. However, two N-acetylgalactosaminyltransferases (xGalNAc-T6 and xGalNAc-T16) from the African clawed frog (Xenopus laevis), which are most homologous to those encoded by the human GALNT6 and GALNT16 (GALNTL1) genes, were shown to have contrasting roles in TGF-β/BMP signaling in embryogenesis. In this study we have examined these two enzymes further and show differences in their in vivo function during X. laevis embyrogenesis as evidenced by in situ hybridization and overexpression experiments. In terms of enzymatic activity, both enzymes were found to be active towards the EA2 peptide, but display differential activity towards a peptide based on the sequence of ActR-IIB, a receptor relevant to TGF-β/BMP signaling. In summary, these data demonstrate that these two enzymes from different branches of the N-acetylgalactosaminyltransferase do not only display differential substrate specificities, but also specific and distinct expression pattern and biological activities in vivo.
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Affiliation(s)
- Josef Voglmeir
- Department für Chemie, Universität für Bodenkultur, Wien, Austria; Manchester Interdisciplinary Biocentre, University of Manchester, UK
| | - Nicolas Laurent
- Manchester Interdisciplinary Biocentre, University of Manchester, UK
| | - Sabine L Flitsch
- Manchester Interdisciplinary Biocentre, University of Manchester, UK
| | | | - Iain B H Wilson
- Department für Chemie, Universität für Bodenkultur, Wien, Austria.
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4
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Bencúr P, Steinkellner H, Svoboda B, Mucha J, Strasser R, Kolarich D, Hann S, Köllensperger G, Glössl J, Altmann F, Mach L. Arabidopsis thaliana beta1,2-xylosyltransferase: an unusual glycosyltransferase with the potential to act at multiple stages of the plant N-glycosylation pathway. Biochem J 2005; 388:515-25. [PMID: 15686448 PMCID: PMC1138959 DOI: 10.1042/bj20042091] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
XylT (beta1,2-xylosyltransferase) is a unique Golgi-bound glycosyltransferase that is involved in the biosynthesis of glycoprotein-bound N-glycans in plants. To delineate the catalytic domain of XylT, a series of N-terminal deletion mutants was heterologously expressed in insect cells. Whereas the first 54 residues could be deleted without affecting the catalytic activity of the enzyme, removal of an additional five amino acids led to the formation of an inactive protein. Characterization of the N-glycosylation status of recombinant XylT revealed that all three potential N-glycosylation sites of the protein are occupied by N-linked oligosaccharides. However, an unglycosylated version of the enzyme displayed substantial catalytic activity, demonstrating that N-glycosylation is not essential for proper folding of XylT. In contrast with most other glycosyltransferases, XylT is enzymatically active in the absence of added metal ions. This feature is not due to any metal ion directly associated with the enzyme. The precise acceptor substrate specificity of XylT was assessed with several physiologically relevant compounds and the xylosylated reaction products were subsequently tested as substrates of other Golgi-resident glycosyltransferases. These experiments revealed that the substrate specificity of XylT permits the enzyme to act at multiple stages of the plant N-glycosylation pathway.
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Affiliation(s)
- Peter Bencúr
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Herta Steinkellner
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Barbara Svoboda
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Jan Mucha
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Richard Strasser
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Daniel Kolarich
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Stephan Hann
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Gunda Köllensperger
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Josef Glössl
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Friedrich Altmann
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Lukas Mach
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
- To whom correspondence should be addressed (email )
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Strasser R, Stadlmann J, Svoboda B, Altmann F, Glössl J, Mach L. Molecular basis of N-acetylglucosaminyltransferase I deficiency in Arabidopsis thaliana plants lacking complex N-glycans. Biochem J 2005; 387:385-91. [PMID: 15537386 PMCID: PMC1134966 DOI: 10.1042/bj20041686] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GnTI (N-acetylglucosaminyltransferase I) is a Golgi-resident enzyme essential for the processing of high-mannose to hybrid and complex N-glycans. The Arabidopsis thaliana cgl mutant lacks GnTI activity and as a consequence accumulates oligomannosidic structures. Molecular cloning of cgl GnTI cDNA revealed a point mutation, which causes a critical amino acid substitution (Asp144-->Asn), thereby creating an additional N-glycosylation site. Heterologous expression of cgl GnTI in insect cells confirmed its lack of activity and the use of the N-glycosylation site. Remarkably, introduction of the Asp144-->Asn mutation into rabbit GnTI, which does not result in the formation of a new N-glycosylation site, led to a protein with strongly reduced, but still detectable enzymic activity. Expression of Asn144 rabbit GnTI in cgl plants could partially restore complex N-glycan formation. These results indicate that the complete deficiency of GnTI activity in cgl plants is mainly due to the additional N-glycan, which appears to interfere with the proper folding of the enzyme.
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Affiliation(s)
- Richard Strasser
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
- To whom correspondence should be addressed (email )
| | - Johannes Stadlmann
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Barbara Svoboda
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Friedrich Altmann
- †Department für Chemie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Josef Glössl
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
| | - Lukas Mach
- *Department für Angewandte Pflanzenwissenschaften und Pflanzenbiotechnologie, Institut für Angewandte Genetik und Zellbiologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
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Müntener K, Willimann A, Zwicky R, Svoboda B, Mach L, Baici A. Folding competence of N-terminally truncated forms of human procathepsin B. J Biol Chem 2005; 280:11973-80. [PMID: 15657038 DOI: 10.1074/jbc.m413052200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Besides acting as an inhibitor, the propeptide of human cathepsin B exerts an important auxiliary function as a chaperone in promoting correct protein folding. To explore the ability of N-terminally truncated forms of procathepsin B to fold into enzymatically active proteins, we produced procathepsin B variants progressively lacking N-terminal structural elements in baculovirus-infected insect cells. N-terminal truncation of the propeptide by up to 22 amino acids did not impair the production of activable procathepsin B. Secreted forms lacking the first 20, 21, or 22 amino acids spontaneously generated mature cathepsin B through autocatalytic processing, demonstrating that the first alpha-helix (Asp11-Arg20) is necessary for efficient inhibition of the enzyme by its propeptide. In contrast, proenzymes lacking the N-terminal part including the first beta-sheet (Trp24-Ala26) of the propeptide or containing an amino acid mutation directly preceding this beta-sheet were no longer properly folded. This shows that interactions between Trp24 of the propeptide and Tyr183, Tyr188, and Phe180 of the mature enzyme are important for stabilization and essential for procathepsin B folding. Thus, proenzyme forms missing more than the N-terminal 22 amino acids of the propeptide (notably truncated cathepsin B produced by the mRNA splice variant lacking exons 2 and 3, resulting in a propeptide shortened by 34 amino acids) are devoid of proteolytic activity because they cannot fold correctly. Thus, any pathophysiological involvement of truncated cathepsin B must be ascribed to properties other than proteolysis.
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Affiliation(s)
- Kathrin Müntener
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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Strasser R, Altmann F, Glössl J, Steinkellner H. Unaltered complex N-glycan profiles in Nicotiana benthamiana despite drastic reduction of beta1,2- N -acetylglucosaminyltransferase I activity. Glycoconj J 2004; 21:275-82. [PMID: 15486460 DOI: 10.1023/b:glyc.0000045099.29038.04] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
UDP-GlcNAc:alpha3-D-mannoside beta1,2- N -acetylglucosaminyltransferase I (GnTI; EC 2.4.1.101) is a Golgi-resident glycosyltransferase that is essential for the processing of oligomannose to hybrid and complex N-glycans in higher eukaryotes. The cDNA of Nicotiana tabacum GnTI has been cloned and characterised previously. To assess the influence of GnTI expression levels on the formation of complex N-glycans we used posttranscriptional gene silencing to knock down the expression of GnTI in the tobacco related species Nicotiana benthamiana. 143 independent transgenic plants containing GnTI constructs in either sense or antisense orientation were generated. 23 lines were selected for measurement of GnTI activity and 10 lines thereof showed a reduction of more than 85% in in vitro assays as compared to wildtype plants. GnTI reduction was stably inherited and did not interfere with the viability of the transformants. Noteworthy one line, 34S/2, exhibited a residual GnTI activity below the detection limit. beta1,2- N -acetylglucosaminyltransferase II (GnTII), an enzyme which acts further downstream in the N-glycosylation pathway, as well as other control enzymes (alpha-mannosidase, beta- N -acetylglucosaminidase) were not affected indicating the specific downregulation of GnTI. Remarkably, immunoblots and mass spectrometric N-glycan profiling revealed no significant changes of the total N-glycan comparable to wildtype plants.
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Affiliation(s)
- Richard Strasser
- Institut für Angewandte Genetik und Zellbiologie, Department für Angewandte Planzenwissenschaften und Pflanzenbiotechnologie, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria.
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Schachter H. The role of the GlcNAc(beta)1,2Man(alpha)- moiety in mammalian development. Null mutations of the genes encoding UDP-N-acetylglucosamine:alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I and UDP-N-acetylglucosamine:alpha-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I.2 cause embryonic lethality and congenital muscular dystrophy in mice and men, respectively. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1573:292-300. [PMID: 12417411 DOI: 10.1016/s0304-4165(02)00396-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The GlcNAc(beta)1,2Man(alpha)- moiety can be synthesized by at least two mammalian glycosyltransferases, UDP-GlcNAc:alpha-3-D-mannoside beta1,2-N-acetylglucosaminyltransferase I (GnT I, EC 2.4.1.101) and UDP-GlcNAc:alpha-D-mannoside beta1,2-N-acetylglucosaminyltransferase I.2 (GnT I.2). GnT I adds a GlcNAc residue in beta1,2 glycosidic linkage to the Man(alpha)1,3 arm of the N-glycan core to initiate the biosynthesis of hybrid and complex N-glycans. GnT I.2 can add GlcNAc in beta1,2 linkage to any alpha-linked terminal Man residue but has a strong preference for the Man(alpha)1-O-Thr- moiety which occurs in alpha-dystroglycan and other O-mannosylated glycoproteins. Mouse embryos lacking a functional GnT I gene (MgatI) were unable to synthesize complex N-glycans and none survived past 10.5 days after fertilization. The embryos showed multisystemic defects in various morphogenic processes such as neural tube formation, vascularization and the determination of left-right body plan asymmetry. Six human patients with muscle-eye-brain disease (MEB) were recently shown to have point mutations in the gene encoding GnT I.2 (MGATI.2). MEB is an autosomal recessive disease characterized by congenital muscular dystrophy, ocular abnormalities, brain malformations and other multisystemic defects. Both the MGATI.2 gene and MEB disease have been mapped to chromosome 1p32-p34. At least one of the biochemical sites affected by the MGATI.2 mutations is probably the interaction between laminin in the extracellular matrix and the peripheral membrane glycoprotein alpha-dystroglycan since this interaction is believed to require the presence of the sialyl(alpha)2,3Gal(beta)1,4GlcNAc(beta)1,2Man(alpha)1-O-Ser/Thr moiety on alpha-dystroglycan. It can be concluded that the GlcNAc(beta)1,2Man(alpha)- moiety is important for mammalian development due to an essential role in two distinct biochemical pathways.
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Affiliation(s)
- Harry Schachter
- Program in Structural Biology and Biochemistry, Hospital for Sick Children, and Department of Biochemistry, University of Toronto, Ontario, Canada.
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Chen S, Tan J, Reinhold VN, Spence AM, Schachter H. UDP-N-acetylglucosamine:alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I and UDP-N-acetylglucosamine:alpha-6-D-mannoside beta-1,2-N-acetylglucosaminyltransferase II in Caenorhabditis elegans. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1573:271-9. [PMID: 12417409 DOI: 10.1016/s0304-4165(02)00393-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
UDP-N-acetylglucosamine:alpha-3-D-mannoside beta-1,2-N-acetylglucosaminyltransferase I (GnT I) and UDP-N-acetylglucosamine:alpha-6-D-mannoside beta-1,2-N-acetylglucosaminyltransferase II (GnT II) are key enzymes in the synthesis of Asn-linked hybrid and complex glycans. We have cloned cDNAs from Caenorhabditis elegans for three genes homologous to mammalian GnT I (designated gly-12, gly-13 and gly-14) and one gene homologous to mammalian GnT II. All four cDNAs encode proteins which have the domain structure typical of previously cloned Golgi-type glycosyltransferases and show enzymatic activity (GnT I and GnT II, respectively) on expression in transgenic worms. We have isolated worm mutants lacking the three GnT I genes by the method of ultraviolet irradiation in the presence of trimethylpsoralen (TMP); null mutants for GnT II have not yet been obtained. The gly-12 and gly-14 mutants as well as the gly-14;gly-12 double mutant displayed wild-type phenotypes indicating that neither gly-12 nor gly-14 is necessary for worm development under standard laboratory conditions. This finding and other data indicate that the GLY-13 protein is the major functional GnT I in C. elegans. The mutation lacking the gly-13 gene is partially lethal and the few survivors display severe morphological and behavioral defects. We have shown that the observed phenotype co-segregates with the gly-13 deletion in genetic mapping experiments although a second mutation near the gly-13 gene cannot as yet be ruled out. Our data indicate that complex and hybrid N-glycans may play critical roles in the morphogenesis of C. elegans, as they have been shown to do in mice and men.
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Affiliation(s)
- Shihao Chen
- Department of Structural Biology and Biochemistry, The Hospital for Sick Children, Toronto, ON, Canada
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Mucha J, Svoboda B, Kappel S, Strasser R, Bencur P, Fröhwein U, Schachter H, Mach L, Glössl J. Two closely related forms of UDP-GlcNAc: alpha6-D-mannoside beta1,2-N-acetylglucosaminyltransferase II occur in the clawed frog Xenopus laevis. Glycoconj J 2002; 19:187-95. [PMID: 12815230 DOI: 10.1023/a:1024201824354] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
UDP-GlcNAc:alpha6-D-mannoside beta1,2-N-acetylglucosaminyltransferase II (GnT II; EC 2.4.1.143) is a medial-Golgi resident enzyme that catalyses an essential step in the biosynthetic pathway leading from high mannose to complex N-linked oligosaccharides. Screening a cDNA library from Xenopus laevis ovary with a human GnT II DNA probe resulted in the isolation of two cDNA clones encoding two closely related GnT II isoenzymes, GnT II-A and GnT II-B. Analysis of the corresponding genomic DNAs revealed that the open reading frame of both X. laevis GnT II genes resides within a single exon. The GnT II-A gene was found to be transcriptionally active in all X. laevis tissues tested. In contrast, expression of the GnT II-B gene was detected only in a limited number of tissues. Both GnT II-A and GnT II-B exhibit a type II transmembrane protein topology with a putative N-terminal cytoplasmic tail of 9 amino acids followed by a transmembrane domain of 18 residues, and a C-terminal luminal domain of 405 residues. The two proteins differ at 28 amino acid positions within their luminal regions. Heterologous expression of soluble forms of the enzymes in insect cells showed that GnT II-A and GnT II-B are both catalytically active and exhibit similar specific activities. Both recombinant proteins are modified with N-linked oligosaccharides. N-terminal deletion studies demonstrated that the first 49 amino acid residues are not essential for proper folding and enzymatic activity of X. laevis GnT II.
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MESH Headings
- Amino Acid Sequence
- Animals
- Baculoviridae/genetics
- Blotting, Northern
- Blotting, Southern
- Blotting, Western
- DNA, Complementary/metabolism
- Electrophoresis, Polyacrylamide Gel
- Exons
- Female
- Gene Library
- Genetic Vectors
- Genome
- Glycosylation
- Golgi Apparatus/metabolism
- Humans
- Insecta
- Molecular Sequence Data
- N-Acetylglucosaminyltransferases/biosynthesis
- N-Acetylglucosaminyltransferases/chemistry
- Oligosaccharides/chemistry
- Ovary/metabolism
- Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase/chemistry
- Polysaccharides/chemistry
- Protein Isoforms
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transcription, Genetic
- Uridine Diphosphate N-Acetylglucosamine/chemistry
- Xenopus laevis
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Affiliation(s)
- Jan Mucha
- Zentrum für Angewandte Genetik, Universität für Bodenkultur Wien, Muthgasse 18, A-1190 Wien, Austria
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