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Yao Q, Gao Y, Zheng N, Delcenserie V, Wang J. Unlocking the mysteries of milk oligosaccharides: Structure, metabolism, and function. Carbohydr Polym 2024; 332:121911. [PMID: 38431414 DOI: 10.1016/j.carbpol.2024.121911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/18/2024] [Accepted: 01/31/2024] [Indexed: 03/05/2024]
Abstract
Milk oligosaccharides (MOs), complex carbohydrates prevalent in human breast milk, play a vital role in infant nutrition. Serving as prebiotics, they inhibit pathogen adherence, modulate the immune system, and support newborn brain development. Notably, MOs demonstrate significant variations in concentration and composition, both across different species and within the same species. These characteristics of MOs lead to several compelling questions: (i) What distinct beneficial functions do MOs offer and how do the functions vary along with their structural differences? (ii) In what ways do MOs in human milk differ from those in other mammals, and what factors drive these unique profiles? (iii) What are the emerging applications of MOs, particularly in the context of their incorporation into infant formula? This review delves into the structural characteristics, quantification methods, and species-specific concentration differences of MOs. It highlights the critical role of human MOs in infant growth and their potential applications, providing substantial evidence to enhance infant health and development.
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Affiliation(s)
- Qianqian Yao
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China; Department of Food Science, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Yanan Gao
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Nan Zheng
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Veronique Delcenserie
- Department of Food Science, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Jiaqi Wang
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China.
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2
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Kobayashi K. Culture Models to Investigate Mechanisms of Milk Production and Blood-Milk Barrier in Mammary Epithelial Cells: a Review and a Protocol. J Mammary Gland Biol Neoplasia 2023; 28:8. [PMID: 37126158 PMCID: PMC10151314 DOI: 10.1007/s10911-023-09536-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 04/21/2023] [Indexed: 05/02/2023] Open
Abstract
Mammary epithelial cells (MECs) are the only cell type that produces milk during lactation. MECs also form less-permeable tight junctions (TJs) to prevent the leakage of milk and blood components through the paracellular pathway (blood-milk barrier). Multiple factors that include hormones, cytokines, nutrition, and temperature regulate milk production and TJ formation in MECs. Multiple intracellular signaling pathways that positively and negatively regulate milk production and TJ formation have been reported. However, their regulatory mechanisms have not been fully elucidated. In addition, unidentified components that regulate milk production in MECs likely exist in foods, for example plants. Culture models of functional MECs that recapitulate milk production and TJs are useful tools for their study. Such models enable the elimination of indirect effects via cells other than MECs and allows for more detailed experimental conditions. However, culture models of MECs with inappropriate functionality may result in unphysiological reactions that never occur in lactating mammary glands in vivo. Here, I briefly review the physiological functions of alveolar MECs during lactation in vivo and culture models of MECs that feature milk production and less-permeable TJs, together with a protocol for establishment of MEC culture with functional TJ barrier and milk production capability using cell culture inserts.
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Affiliation(s)
- Ken Kobayashi
- Laboratory of Cell and Tissue Biology, Research Faculty of Agriculture, Hokkaido University, North 9, West 9, Sapporo, 060-8589, Japan.
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3
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Unusual free oligosaccharides in human bovine and caprine milk. Sci Rep 2022; 12:10790. [PMID: 35750794 PMCID: PMC9232581 DOI: 10.1038/s41598-022-15140-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/20/2022] [Indexed: 11/23/2022] Open
Abstract
Free oligosaccharides are abundant macronutrients in milk and involved in prebiotic functions and antiadhesive binding of viruses and pathogenic bacteria to colonocytes. Despite the importance of these oligosaccharides, structural determination of oligosaccharides is challenging, and milk oligosaccharide biosynthetic pathways remain unclear. Oligosaccharide structures are conventionally determined using a combination of chemical reactions, exoglycosidase digestion, nuclear magnetic resonance spectroscopy, and mass spectrometry. Most reported free oligosaccharides are highly abundant and have lactose at the reducing end, and current oligosaccharide biosynthetic pathways in human milk are proposed based on these oligosaccharides. In this study, a new mass spectrometry technique, which can identify linkages, anomericities, and stereoisomers, was applied to determine the structures of free oligosaccharides in human, bovine, and caprine milk. Oligosaccharides that do not follow the current biosynthetic pathways and are not synthesized by any discovered enzymes were found, indicating the existence of undiscovered biosynthetic pathways and enzymes.
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4
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Tvaroška I. Glycosyltransferases as targets for therapeutic intervention in cancer and inflammation: molecular modeling insights. CHEMICAL PAPERS 2022. [DOI: 10.1007/s11696-021-02026-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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5
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García-García A, Hicks T, El Qaidi S, Zhu C, Hardwidge PR, Angulo J, Hurtado-Guerrero R. NleB/SseK-catalyzed arginine-glycosylation and enteropathogen virulence are finely tuned by a single variable position contiguous to the catalytic machinery. Chem Sci 2021; 12:12181-12191. [PMID: 34667584 PMCID: PMC8457375 DOI: 10.1039/d1sc04065k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 08/12/2021] [Indexed: 01/18/2023] Open
Abstract
NleB/SseK effectors are arginine-GlcNAc-transferases expressed by enteric bacterial pathogens that modify host cell proteins to disrupt signaling pathways. While the conserved Citrobacter rodentium NleB and E. coli NleB1 proteins display a broad selectivity towards host proteins, Salmonella enterica SseK1, SseK2, and SseK3 have a narrowed protein substrate selectivity. Here, by combining computational and biophysical experiments, we demonstrate that the broad protein substrate selectivity of NleB relies on Tyr284NleB/NleB1, a second-shell residue contiguous to the catalytic machinery. Tyr284NleB/NleB1 is important in coupling protein substrate binding to catalysis. This is exemplified by S286YSseK1 and N302YSseK2 mutants, which become active towards FADD and DR3 death domains, respectively, and whose kinetic properties match those of enterohemorrhagic E. coli NleB1. The integration of these mutants into S. enterica increases S. enterica survival in macrophages, suggesting that better enzymatic kinetic parameters lead to enhanced virulence. Our findings provide insights into how these enzymes finely tune arginine-glycosylation and, in turn, bacterial virulence. In addition, our data show how promiscuous glycosyltransferases preferentially glycosylate specific protein substrates. The NleB and SseK glycosyltransferases glycosylate arginine residues of mammalian proteins with different substrate specificities. We uncover that these differences rely on a particular second-shell residue contiguous to the catalytic machinery.![]()
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Affiliation(s)
- Ana García-García
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D Zaragoza Spain
| | - Thomas Hicks
- School of Pharmacy, University of East Anglia Norwich Research Park Norwich NR4 7TJ UK
| | - Samir El Qaidi
- College of Veterinary Medicine, Kansas State University Manhattan KS 66506 USA
| | - Congrui Zhu
- College of Veterinary Medicine, Kansas State University Manhattan KS 66506 USA
| | - Philip R Hardwidge
- College of Veterinary Medicine, Kansas State University Manhattan KS 66506 USA
| | - Jesús Angulo
- School of Pharmacy, University of East Anglia Norwich Research Park Norwich NR4 7TJ UK.,Departamento de Química Orgánica, Universidad de Sevilla Sevilla 41012 Spain .,Instituto de Investigaciones Químicas (CSIC-US) Sevilla 41092 Spain
| | - Ramon Hurtado-Guerrero
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D Zaragoza Spain .,Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen Copenhagen Denmark.,Fundación ARAID Zaragoza Spain
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6
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García-García A, Serna S, Yang Z, Delso I, Taleb V, Hicks T, Artschwager R, Vakhrushev SY, Clausen H, Angulo J, Corzana F, Reichardt NC, Hurtado-Guerrero R. FUT8-Directed Core Fucosylation of N-glycans Is Regulated by the Glycan Structure and Protein Environment. ACS Catal 2021; 11:9052-9065. [PMID: 35662980 PMCID: PMC9161449 DOI: 10.1021/acscatal.1c01698] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 06/24/2021] [Indexed: 12/17/2022]
Abstract
FUT8 is an essential α-1,6-fucosyltransferase that fucosylates the innermost GlcNAc of N-glycans, a process called core fucosylation. In vitro, FUT8 exhibits substrate preference for the biantennary complex N-glycan oligosaccharide (G0), but the role of the underlying protein/peptide to which N-glycans are attached remains unclear. Here, we explored the FUT8 enzyme with a series of N-glycan oligosaccharides, N-glycopeptides, and an Asn-linked oligosaccharide. We found that the underlying peptide plays a role in fucosylation of paucimannose (low mannose) and high-mannose N-glycans but not for complex-type N-glycans. Using saturation transfer difference (STD) NMR spectroscopy, we demonstrate that FUT8 recognizes all sugar units of the G0 N-glycan and most of the amino acid residues (Asn-X-Thr) that serve as a recognition sequon for the oligosaccharyltransferase (OST). The largest STD signals were observed in the presence of GDP, suggesting that prior FUT8 binding to GDP-β-l-fucose (GDP-Fuc) is required for an optimal recognition of N-glycans. We applied genetic engineering of glycosylation capacities in CHO cells to evaluate FUT8 core fucosylation of high-mannose and complex-type N-glycans in cells with a panel of well-characterized therapeutic N-glycoproteins. This confirmed that core fucosylation mainly occurs on complex-type N-glycans, although clearly only at selected glycosites. Eliminating the capacity for complex-type glycosylation in cells (KO mgat1) revealed that glycosites with complex-type N-glycans when converted to high mannose lost the core Fuc. Interestingly, however, for erythropoietin that is uncommon among the tested glycoproteins in efficiently acquiring tetra-antennary N-glycans, two out of three N-glycosites obtained Fuc on the high-mannose N-glycans. An examination of the N-glycosylation sites of several protein crystal structures indicates that core fucosylation is mostly affected by the accessibility and nature of the N-glycan and not by the nature of the underlying peptide sequence. These data have further elucidated the different FUT8 acceptor substrate specificities both in vitro and in vivo in cells, revealing different mechanisms for promoting core fucosylation.
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Affiliation(s)
- Ana García-García
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza 50018, Spain
| | - Sonia Serna
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo Miramón 182, Donostia San Sebastián 20014, Spain
| | - Zhang Yang
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Ignacio Delso
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Víctor Taleb
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza 50018, Spain
| | - Thomas Hicks
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Raik Artschwager
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo Miramón 182, Donostia San Sebastián 20014, Spain
| | - Sergey Y Vakhrushev
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Henrik Clausen
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Jesús Angulo
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,Departamento de Química Orgánica, Universidad de Sevilla, Sevilla 41012, Spain.,Instituto de Investigaciones Químicas (CSIC-US), Avda. Américo Vespucio, 49, Seville 41092, Spain
| | - Francisco Corzana
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, Logroño E-26006, Spain
| | - Niels C Reichardt
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo Miramón 182, Donostia San Sebastián 20014, Spain.,CIBER-BBN, Paseo Miramón 182, San Sebastian 20014, Spain
| | - Ramon Hurtado-Guerrero
- Institute of Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Mariano Esquillor s/n, Campus Rio Ebro, Edificio I+D, Zaragoza 50018, Spain.,Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen DK-2200, Denmark.,Fundación ARAID, Zaragoza 50018, Spain
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7
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Sadovnikova A, Garcia SC, Hovey RC. A Comparative Review of the Cell Biology, Biochemistry, and Genetics of Lactose Synthesis. J Mammary Gland Biol Neoplasia 2021; 26:181-196. [PMID: 34125364 PMCID: PMC8236053 DOI: 10.1007/s10911-021-09490-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 05/20/2021] [Indexed: 12/18/2022] Open
Abstract
Lactose is the primary carbohydrate in the milk of most mammals and is unique in that it is only synthesized by epithelial cells in the mammary glands. Lactose is also essential for the development and nutrition of infants. Across species, the concentration of lactose in milk holds a strong positive correlation with overall milk volume. Additionally, there is a range of examples where the onset of lactose synthesis as well as the content of lactose in milk varies between species and throughout a lactation. Despite this diversity, the precursors, genes, proteins and ions that regulate lactose synthesis have not received the depth of study they likely deserve relative to the significance of this simple and abundant molecule. Through this review, our objective is to highlight the requirements for lactose synthesis at the biochemical, cellular and temporal levels through a comparative approach. This overview also serves as the prelude to a companion review describing the dietary, hormonal, molecular, and genetic factors that regulate lactose synthesis.
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Affiliation(s)
- Anna Sadovnikova
- Graduate Group in Nutritional Biology, Physician Scientist Training Program, University of California, Davis, CA, USA.
- Department of Animal Science, University of California, Davis, CA, USA.
| | - Sergio C Garcia
- School of Life and Environmental Sciences, University of Sydney, Sydney, Australia
| | - Russell C Hovey
- Department of Animal Science, University of California, Davis, CA, USA
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8
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α-Lactalbumin, Amazing Calcium-Binding Protein. Biomolecules 2020; 10:biom10091210. [PMID: 32825311 PMCID: PMC7565966 DOI: 10.3390/biom10091210] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4–5), Ca2+-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of α-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. α-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of α-LA can be used in practical applications such as drug delivery to tissues and organs. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid are cytotoxic to various tumor and bacterial cells. α-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of α-LA with oleic acid will be used for development of new anti-cancer drugs.
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9
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Harrus D, Khoder-Agha F, Peltoniemi M, Hassinen A, Ruddock L, Kellokumpu S, Glumoff T. The dimeric structure of wild-type human glycosyltransferase B4GalT1. PLoS One 2018; 13:e0205571. [PMID: 30352055 PMCID: PMC6198961 DOI: 10.1371/journal.pone.0205571] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 09/27/2018] [Indexed: 11/26/2022] Open
Abstract
Most glycosyltransferases, including B4GalT1 (EC 2.4.1.38), are known to assemble into enzyme homomers and functionally relevant heteromers in vivo. However, it remains unclear why and how these enzymes interact at the molecular/atomic level. Here, we solved the crystal structure of the wild-type human B4GalT1 homodimer. We also show that B4GalT1 exists in a dynamic equilibrium between monomer and dimer, since a purified monomer reappears as a mixture of both and as we obtained crystal forms of the monomer and dimer assemblies in the same crystallization conditions. These two crystal forms revealed the unliganded B4GalT1 in both the open and the closed conformation of the Trp loop and the lid regions, responsible for donor and acceptor substrate binding, respectively. The present structures also show the lid region in full in an open conformation, as well as a new conformation for the GlcNAc acceptor loop (residues 272–288). The physiological relevance of the homodimer in the crystal was validated by targeted mutagenesis studies coupled with FRET assays. These showed that changing key catalytic amino acids impaired homomer formation in vivo. The wild-type human B4GalT1 structure also explains why the variant proteins used for crystallization in earlier studies failed to reveal the homodimers described in this study.
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Affiliation(s)
- Deborah Harrus
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Fawzi Khoder-Agha
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Miika Peltoniemi
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Antti Hassinen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Lloyd Ruddock
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Sakari Kellokumpu
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
| | - Tuomo Glumoff
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7A, Oulu, Finland
- * E-mail:
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10
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de Las Rivas M, Coelho H, Diniz A, Lira-Navarrete E, Compañón I, Jiménez-Barbero J, Schjoldager KT, Bennett EP, Vakhrushev SY, Clausen H, Corzana F, Marcelo F, Hurtado-Guerrero R. Structural Analysis of a GalNAc-T2 Mutant Reveals an Induced-Fit Catalytic Mechanism for GalNAc-Ts. Chemistry 2018; 24:8382-8392. [PMID: 29601100 DOI: 10.1002/chem.201800701] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Indexed: 02/02/2023]
Abstract
The family of polypeptide N-acetylgalactosamine (GalNAc) transferases (GalNAc-Ts) orchestrates the initiating step of mucin-type protein O-glycosylation by transfer of GalNAc moieties to serine and threonine residues in proteins. Deficiencies and dysregulation of GalNAc-T isoenzymes are related to different diseases. Recently, it has been demonstrated that an inactive GalNAc-T2 mutant (F104S), which is not located at the active site, induces low levels of high-density lipoprotein cholesterol (HDL-C) in humans. Herein, the molecular basis for F104S mutant inactivation has been deciphered. Saturation transfer difference NMR spectroscopy experiments demonstrate that the mutation induces loss of binding to peptide substrates. Analysis of the crystal structure of the F104S mutant bound to UDP-GalNAc (UDP=uridine diphosphate), combined with molecular dynamics (MD) simulations, has revealed that the flexible loop is disordered and displays larger conformational changes in the mutant enzyme than that in the wild-type (WT) enzyme. 19 F NMR spectroscopy experiments reveal that the WT enzyme only reaches the active state in the presence of UDP-GalNAc, which provides compelling evidence that GalNAc-T2 adopts a UDP-GalNAc-dependent induced-fit mechanism. The F104S mutation precludes the enzyme from achieving the active conformation and concomitantly binding peptide substrates. This study provides new insights into the catalytic mechanism of the large family of GalNAc-Ts and how these enzymes orchestrate protein O-glycosylation.
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Affiliation(s)
- Matilde de Las Rivas
- Instituto de Biocomputación y Fisica de Sistemas Complejos (BIFI), BIFI-IQFR (CSIC) Joint Unit, Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - Helena Coelho
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
- CIC bioGUNE, Bizkaia Technology Park, Building 801A, 48170, Derio, Spain
- Department of Organic Chemistry II, Faculty of Science & Technology, University of the Basque Country, 48940, Leioa, Bizkaia, Spain
| | - Ana Diniz
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
| | - Erandi Lira-Navarrete
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen, Copenhagen, Denmark
| | - Ismael Compañón
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, E-26006, Logroño, Spain
| | - Jesús Jiménez-Barbero
- CIC bioGUNE, Bizkaia Technology Park, Building 801A, 48170, Derio, Spain
- Department of Organic Chemistry II, Faculty of Science & Technology, University of the Basque Country, 48940, Leioa, Bizkaia, Spain
- Ikerbasque, Basque Foundation for Science, Maria Diaz de Haro 13, 48009, Bilbao, Spain
| | - Katrine T Schjoldager
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen, Copenhagen, Denmark
| | - Eric P Bennett
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen, Copenhagen, Denmark
| | - Sergey Y Vakhrushev
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen, Copenhagen, Denmark
| | - Henrik Clausen
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, School of Dentistry, University of Copenhagen, Copenhagen, Denmark
| | - Francisco Corzana
- Departamento de Química, Universidad de La Rioja, Centro de Investigación en Síntesis Química, E-26006, Logroño, Spain
| | - Filipa Marcelo
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
| | - Ramon Hurtado-Guerrero
- Instituto de Biocomputación y Fisica de Sistemas Complejos (BIFI), BIFI-IQFR (CSIC) Joint Unit, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Fundación ARAID, 50018, Zaragoza, Spain
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11
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Balogh R, Jankovics P, Béni S. Qualitative and quantitative analysis of N -acetyllactosamine and lacto- N -biose, the two major building blocks of human milk oligosaccharides in human milk samples by high-performance liquid chromatography–tandem mass spectrometry using a porous graphitic carbon column. J Chromatogr A 2015; 1422:140-146. [DOI: 10.1016/j.chroma.2015.10.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 10/03/2015] [Accepted: 10/05/2015] [Indexed: 01/07/2023]
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12
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Abstract
Human milk oligosaccharides (HMOs) are a family of structurally diverse unconjugated glycans that are highly abundant in and unique to human milk. Originally, HMOs were discovered as a prebiotic "bifidus factor" that serves as a metabolic substrate for desired bacteria and shapes an intestinal microbiota composition with health benefits for the breast-fed neonate. Today, HMOs are known to be more than just "food for bugs". An accumulating body of evidence suggests that HMOs are antiadhesive antimicrobials that serve as soluble decoy receptors, prevent pathogen attachment to infant mucosal surfaces and lower the risk for viral, bacterial and protozoan parasite infections. In addition, HMOs may modulate epithelial and immune cell responses, reduce excessive mucosal leukocyte infiltration and activation, lower the risk for necrotizing enterocolitis and provide the infant with sialic acid as a potentially essential nutrient for brain development and cognition. Most data, however, stem from in vitro, ex vivo or animal studies and occasionally from association studies in mother-infant cohorts. Powered, randomized and controlled intervention studies will be needed to confirm relevance for human neonates. The first part of this review introduces the pioneers in HMO research, outlines HMO structural diversity and describes what is known about HMO biosynthesis in the mother's mammary gland and their metabolism in the breast-fed infant. The second part highlights the postulated beneficial effects of HMO for the breast-fed neonate, compares HMOs with oligosaccharides in the milk of other mammals and in infant formula and summarizes the current roadblocks and future opportunities for HMO research.
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Affiliation(s)
- Lars Bode
- Division of Neonatology and Division of Gastroenterology and Nutrition, Department of Pediatrics, University of California, San Diego, CA, USA.
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13
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Association of polymorphism of the β(1, 4)-galactosyltransferase-I gene with milk production traits in Holsteins. Mol Biol Rep 2012; 39:6715-21. [DOI: 10.1007/s11033-012-1495-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 01/24/2012] [Indexed: 10/14/2022]
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Kraft B, Johswich A, Kauczor G, Scharenberg M, Gerardy-Schahn R, Bakker H. "Add-on" domains of Drosophila β1,4-N-acetylgalactosaminyltransferase B in the stem region and its pilot protein. Cell Mol Life Sci 2011; 68:4091-100. [PMID: 21598021 PMCID: PMC11114974 DOI: 10.1007/s00018-011-0725-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 04/27/2011] [Accepted: 05/03/2011] [Indexed: 01/10/2023]
Abstract
The glycolipid specific Drosophila melanogaster β1,4-N-acetylgalactosaminyltransferase B (β4GalNAcTB) depends on a zinc finger DHHC protein family member named GalNAcTB pilot (GABPI) for activity and translocation to the Golgi. The six-membrane spanning protein actually lacks the cysteine in the cytoplasmic DHHC motif, displaying DHHS instead. Here we show that the whole conserved region around the DHHS sequence, which is essential for palmitoylation in DHHC proteins, is not required for GABPI to interact with β4GalNAcTB. In contrast, the two luminal loops between transmembrane domain 3-4 and 5-6 contain conserved amino acids, which are crucial for activity. Besides the dependence on GABPI, β4GalNAcTB requires its exceptional short stem region for activity. A few hydrophobic amino acids positioned close to the transmembrane domain are essential for the interaction with GABPI. Along with its catalytic domain, β4GalNAcTB, thus, requires an area in its own stem region and two small luminal loops of GABPI as "add-on" domains. Moreover, some inactive GABPI mutants could be rescued by fusion with β4GalNAcTB, indicating their importance in direct GABPI-β4GalNAcTB interaction.
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Affiliation(s)
- Benjamin Kraft
- Department of Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Anita Johswich
- Present Address: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue R988, Toronto, ON M5G 1X5 Canada
| | - Gwenda Kauczor
- Department of Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Meike Scharenberg
- Present Address: Institute of Molecular Pharmacy, Pharmacenter, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Rita Gerardy-Schahn
- Department of Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Hans Bakker
- Department of Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
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15
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Medinas DB, Gozzo FC, Santos LFA, Iglesias AH, Augusto O. A ditryptophan cross-link is responsible for the covalent dimerization of human superoxide dismutase 1 during its bicarbonate-dependent peroxidase activity. Free Radic Biol Med 2010; 49:1046-53. [PMID: 20600836 DOI: 10.1016/j.freeradbiomed.2010.06.018] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Revised: 06/14/2010] [Accepted: 06/16/2010] [Indexed: 12/28/2022]
Abstract
Unlike intermolecular disulfide bonds, other protein cross-links arising from oxidative modifications cannot be reversed and are presumably more toxic to cells because they may accumulate and induce protein aggregation. However, most of these irreversible protein cross-links remain poorly characterized. For instance, the antioxidant enzyme human superoxide dismutase 1 (hSod1) has been reported to undergo non-disulfide covalent dimerization and further oligomerization during its bicarbonate-dependent peroxidase activity. The dimerization was shown to be dependent on the oxidation of the single, solvent-exposed Trp(32) residue of hSod1, but the covalent dimer was not isolated nor was its structure determined. In this work, the hSod1 covalent dimer was isolated, digested with trypsin in H(2)O and H(2)(18)O, and analyzed by UV-Vis spectroscopy and mass spectrometry (MS). The results demonstrate that the covalent dimer consists of two hSod1 subunits cross-linked by a ditryptophan, which contains a bond between C3 and N1 of the respective Trp(32) residues. We further demonstrate that the cross-link cleaves under usual MS/MS conditions leading to apparently unmodified Trp(32), partially hinders proteolysis, and provides a mechanism to explain the formation of hSod1 covalent trimers and tetramers. This characterization of the covalent hSod1 dimer identifies a novel oxidative modification of protein Trp residues and provides clues for studying its occurrence in vivo.
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Affiliation(s)
- Danilo B Medinas
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05513-970 São Paulo, SP, Brazil.
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Harholt J, Suttangkakul A, Vibe Scheller H. Biosynthesis of pectin. PLANT PHYSIOLOGY 2010; 153:384-95. [PMID: 20427466 PMCID: PMC2879803 DOI: 10.1104/pp.110.156588] [Citation(s) in RCA: 335] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 04/27/2010] [Indexed: 05/17/2023]
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Littlejohn MD, Walker CG, Ward HE, Lehnert KB, Snell RG, Verkerk GA, Spelman RJ, Clark DA, Davis SR. Effects of reduced frequency of milk removal on gene expression in the bovine mammary gland. Physiol Genomics 2009; 41:21-32. [PMID: 19996161 DOI: 10.1152/physiolgenomics.00108.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Regulation of milk synthesis and secretion is controlled mostly through local (intramammary) mechanisms. To gain insight into the molecular pathways comprising this response, an analysis of mammary gene expression was conducted in 12 lactating cows shifted from twice daily to once daily milking. Tissues were sampled by biopsy from adjacent mammary quarters of these animals during the two milking frequencies, allowing changes in gene expression to be assessed within each animal. Using bovine-specific, oligonucleotide arrays representing 21,495 unique transcripts, a range of differentially expressed genes were found as a result of less frequent milk removal, constituting transcripts and pathways related to apoptotic signaling (NF-kappaB, JUN, ATF3, IGFBP5, TNFSF12A) mechanical stress and epithelial tight junction synthesis (CYR61, CTGF, THBS1, CLDN4, CLDN8), and downregulated milk synthesis (LALBA, B4GALT1, UGP2, CSN2, GPAM, LPL). Quantitative real-time PCR was used to assess the expression of 13 genes in the study, and all 13 of these were correlated (P < 0.05) with values derived from array analysis. It can be concluded that the physiological changes that occur in the bovine mammary gland as a result of reduced milk removal frequency likely comprise the earliest stages of the involution response and that mechano-signal transduction cascades associated with udder distension may play a role in triggering these events.
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Krupička M, Tvaroška I. Hybrid Quantum Mechanical/Molecular Mechanical Investigation of the β-1,4-Galactosyltransferase-I Mechanism. J Phys Chem B 2009; 113:11314-9. [DOI: 10.1021/jp904716t] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Martin Krupička
- Contribution from the Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravska cesta 9, 845 38 Bratislava, Slovak Republic
| | - Igor Tvaroška
- Contribution from the Institute of Chemistry, Centre for Glycomics, Slovak Academy of Sciences, Dúbravska cesta 9, 845 38 Bratislava, Slovak Republic
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20
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Johswich A, Kraft B, Wuhrer M, Berger M, Deelder AM, Hokke CH, Gerardy-Schahn R, Bakker H. Golgi targeting of Drosophila melanogaster beta4GalNAcTB requires a DHHC protein family-related protein as a pilot. ACTA ACUST UNITED AC 2009; 184:173-83. [PMID: 19139268 PMCID: PMC2615082 DOI: 10.1083/jcb.200801071] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Drosophila melanogaster β4GalNAcTB mutant flies revealed that this particular N-acetylgalactosaminyltransferase is predominant in the formation of lacdiNAc (GalNAcβ1,4GlcNAc)-modified glycolipids, but enzymatic activity could not be confirmed for the cloned enzyme. Using a heterologous expression cloning approach, we isolated β4GalNAcTB together with β4GalNAcTB pilot (GABPI), a multimembrane-spanning protein related to Asp-His-His-Cys (DHHC) proteins but lacking the DHHC consensus sequence. In the absence of GABPI, inactive β4GalNAcTB is trapped in the endoplasmic reticulum (ER). Coexpression of β4GalNAcTB and GABPI generates the active enzyme that is localized together with GABPI in the Golgi. GABPI associates with β4GalNAcTB and, when expressed with an ER retention signal, holds active β4GalNAcTB in the ER. Importantly, treatment of isolated membrane vesicles with Triton X-100 disturbs β4GalNAcTB activity. This phenomenon occurs with multimembrane-spanning glycosyltransferases but is normally not a property of glycosyltransferases with one membrane anchor. In summary, our data provide evidence that GABPI is required for ER export and activity of β4GalNAcTB.
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Affiliation(s)
- Anita Johswich
- Department of Cellular Chemistry, Hannover Medical School, Hannover, Germany
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21
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Qasba PK, Ramakrishnan B, Boeggeman E. Structure and function of beta -1,4-galactosyltransferase. Curr Drug Targets 2008; 9:292-309. [PMID: 18393823 DOI: 10.2174/138945008783954943] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Beta-1,4-galactosylransferase (beta4Gal-T1) participates in the synthesis of Galbeta1-4-GlcNAc-disaccharide unit of glycoconjugates. It is a trans-Golgi glycosyltransferase (Glyco-T) with a type II membrane protein topology, a short N-terminal cytoplasmic domain, a membrane-spanning region, as well as a stem and a C-terminal catalytic domain facing the trans-Golgi-lumen. Its hydrophobic membrane-spanning region, like that of other Glyco-T, has a shorter length compared to plasma membrane proteins, an important feature for its retention in the trans-Golgi. The catalytic domain has two flexible loops, a long and a small one. The primary metal binding site is located at the N-terminal hinge region of the long flexible loop. Upon binding of metal ion and sugar-nucleotide, the flexible loops undergo a marked conformational change, from an open to a closed conformation. Conformational change simultaneously creates at the C-terminal region of the flexible loop an oligosaccharide acceptor binding site that did not exist before. The loop acts as a lid covering the bound donor substrate. After completion of the transfer of the glycosyl unit to the acceptor, the saccharide product is ejected; the loop reverts to its native conformation to release the remaining nucleotide moiety. The conformational change in beta4Gal-T1 also creates the binding site for a mammary gland-specific protein, alpha-lactalbumin (LA), which changes the acceptor specificity of the enzyme toward glucose to synthesize lactose during lactation. The specificity of the sugar donor is generally determined by a few residues in the sugar-nucleotide binding pocket of Glyco-T, conserved among the family members from different species. Mutation of these residues has allowed us to design new and novel glycosyltransferases, with broader or requisite donor and acceptor specificities, and to synthesize specific complex carbohydrates as well as specific inhibitors for these enzymes.
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Affiliation(s)
- Pradman K Qasba
- Structural Glycobiology Section, CCRNP, NCI-Frederick, Building 469, Room 221, Frederick, Maryland 21702, USA.
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22
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Yamakura F, Ikeda K, Matsumoto T, Taka H, Kaga N. Formation of 6-nitrotryptophan in purified proteins by reactive nitrogen species: A possible new biomarker. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.ics.2007.07.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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23
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Qasba PK, Ramakrishnan B. Letter to the Glyco-Forum: Catalytic domains of glycosyltransferases with ‘add-on’ domains. Glycobiology 2007; 17:7G-9G. [PMID: 17283039 DOI: 10.1093/glycob/cwm013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Berg S, Kaur D, Jackson M, Brennan PJ. The glycosyltransferases of Mycobacterium tuberculosis - roles in the synthesis of arabinogalactan, lipoarabinomannan, and other glycoconjugates. Glycobiology 2007; 17:35-56R. [PMID: 17261566 DOI: 10.1093/glycob/cwm010] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Several human pathogens are to be found within the bacterial genus Mycobacterium, notably Mycobacterium tuberculosis, the causative agent of tuberculosis, one of the most threatening of human infectious diseases, with an annual lethality of about two million people. The characteristic mycobacterial cell envelope is the dominant feature of the biology of M. tuberculosis and other mycobacterial pathogens, based on sugars and lipids of exceptional structure. The cell wall consists of a peptidoglycan-arabinogalactan-mycolic acid complex beyond the plasma membrane. Free-standing lipids, lipoglycans, and proteins intercalate within this complex, complement the mycolic acid monolayer and may also appear in a capsular-like arrangement. The consequences of these structural oddities are an extremely robust and impermeable cell envelope. This review reflects on these entities from the perspective of their synthesis, particularly the structural and functional aspects of the glycosyltransferases (GTs) of M. tuberculosis, the dominating group of enzymes responsible for the terminal stages of their biosynthesis. Besides the many nucleotide-sugar dependent GTs with orthologs in prokaryotes and eukaryotes, M. tuberculosis and related species of the order Actinomycetales, in light of the highly lipophilic environment prevailing within the cell envelope, carry a significant number of GTs of the GT-C class dependent on polyprenyl-phosphate-linked sugars. These are of special emphasis in this review.
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Affiliation(s)
- Stefan Berg
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA
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25
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Yamakura F, Ikeda K. Modification of tryptophan and tryptophan residues in proteins by reactive nitrogen species. Nitric Oxide 2006; 14:152-61. [PMID: 16140551 DOI: 10.1016/j.niox.2005.07.009] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 07/21/2005] [Accepted: 07/24/2005] [Indexed: 11/16/2022]
Abstract
Formation of 3-nitrotyrosine by the reaction between reactive nitrogen species (RNS) and tyrosine residues in proteins has been analyzed extensively and it is used widely as a biomarker of pathophysiological and physiological conditions mediated by RNS. In contrast, few studies on the nitration of tryptophan have been reported. This review provides an overview of the studies on tryptophan modifications by RNS and points out the possible importance of its modification in pathophysiological and physiological conditions. Free tryptophan can be modified to several nitrated products (1-, 4-, 5-, 6-, and 7-), 1-N-nitroso product, and several oxidized products by reaction with various RNS, depending on the conditions used. Among them, 1-N-nitrosotryptophan and 6-nitrotryptophan (6-NO(2)Trp) have been found as the abundant products in the reaction with peroxynitrite, and 6-NO(2)Trp has been the most abundant product in the reaction with the peroxidase/hydrogen peroxide/nitrite systems. 6-NO(2)Trp has also been observed as the most abundant nitrated product of the reactions between peroxynitrite or myeloperoxidase/hydrogen peroxide/nitrite and tryptophan residues both in human Cu,Zn-superoxide dismutase and in bovine serum albumin, as well as the reaction of peroxynitrite with myoglobin and hemoglobin. Several oxidized products have also been identified in the modified Cu,Zn-SOD. However, no 1-N-nitrosotryptophan and 1-N-nitrotryptophan has been observed in the proteins reacted with peroxynitrite or the myeloperoxidase/H(2)O(2)/nitrite system. The modification of tryptophan residues in proteins may occur at a more limited number of sites in vivo than that of tyrosine residues, since tryptophan residues are more buried inside proteins and exist less frequently in proteins, generally. However, surface-exposed tryptophan residues tend to participate in the interaction with the other molecules, therefore the modification of those tryptophans may result in modulation of the specific interaction of proteins and enzymes with other molecules.
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Affiliation(s)
- Fumiyuki Yamakura
- Department of Chemistry, Juntendo University School of Medicine, 1-1 Hiragagakuendai, Inba, Chiba 270-1606, Japan.
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26
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Fast J, Mossberg AK, Svanborg C, Linse S. Stability of HAMLET--a kinetically trapped alpha-lactalbumin oleic acid complex. Protein Sci 2005; 14:329-40. [PMID: 15659367 PMCID: PMC2253409 DOI: 10.1110/ps.04982905] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The stability toward thermal and urea denaturation was measured for HAMLET (human alpha-lactalbumin made lethal to tumor cells) and alpha-lactalbumin, using circular dichroism and fluorescence spectroscopy as well as differential scanning calorimetry. Under all conditions examined, HAMLET appears to have the same or lower stability than alpha-lactalbumin. The largest difference is seen for thermal denaturation of the calcium free (apo) forms, where the temperature at the transition midpoint is 15 degrees C lower for apo HAMLET than for apo alpha-lactalbumin. The difference becomes progressively smaller as the calcium concentration increases. Denaturation of HAMLET was found to be irreversible. Samples of HAMLET that have been renatured after denaturation have lost the specific biological activity toward tumor cells. Three lines of evidence indicate that HAMLET is a kinetic trap: (1) It has lower stability than alpha-lactalbumin, although it is a complex of alpha-lactalbumin and oleic acid; (2) its denaturation is irreversible and HAMLET is lost after denaturation; (3) formation of HAMLET requires a specific conversion protocol.
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Affiliation(s)
- Jonas Fast
- Department of Chemistry and Biochemistry, University of Colorado, Cristol Building, Room 226, Boulder, CO 80309-0215, USA.
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27
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Qasba PK, Ramakrishnan B, Boeggeman E. Substrate-induced conformational changes in glycosyltransferases. Trends Biochem Sci 2005; 30:53-62. [PMID: 15653326 DOI: 10.1016/j.tibs.2004.11.005] [Citation(s) in RCA: 186] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oligosaccharide chains of glycoproteins, glycolipids and glycosaminoglycans are synthesized by glycosyltransferases by the transfer of specific glycosyl moieties from activated sugar-nucleotide donors to specific acceptors. Structural studies on several of these enzymes have shown that one or two flexible loops at the substrate-binding site of the enzymes undergo a marked conformational change from an open to a closed conformation on binding the donor substrate. This conformational change, in which the loop acts as a lid covering the bound donor substrate, creates an acceptor-binding site. After the glycosyl unit is transferred from the donor to the acceptor, the saccharide product is ejected and the loop reverts to its native conformation, thereby releasing the remaining nucleotide moiety. The specificity of the sugar donor is determined by a few residues in the sugar-nucleotide-binding pocket of the enzyme that are conserved among the family members from different species.
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Affiliation(s)
- Pradman K Qasba
- Structural Glycobiology Section, Laboratory of Experimental and Computational Biology, CCR, NCI-Frederick, MD 21702, USA.
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Ramakrishnan B, Boeggeman E, Ramasamy V, Qasba PK. Structure and catalytic cycle of β-1,4-galactosyltransferase. Curr Opin Struct Biol 2004; 14:593-600. [PMID: 15465321 DOI: 10.1016/j.sbi.2004.09.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Beta-1,4-galactosyltransferase-1, a housekeeping enzyme that functions in the synthesis of glycoconjugates, has two flexible loops, one short and one long. Upon binding a metal ion and UDP-galactose, the loops change from an open to a closed conformation, repositioning residues to lock the ligands in place. Residues at the N-terminal region of the long loop form the metal-binding site and those at the C-terminal region form a helix, which becomes part of the binding site for the oligosaccharide acceptor; the remaining residues cover the bound sugar-nucleotide. After binding of the oligosaccharide acceptor and transfer of the galactose moiety, the product disaccharide unit is ejected and the enzyme returns to the open conformation, repeating the catalytic cycle.
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Affiliation(s)
- Boopathy Ramakrishnan
- Structural Glycobiology Section, Laboratory of Experimental and Computational Biology, Center for Cancer Research, NCI-Frederick, MD 21702, USA
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29
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Griffitts JS, Huffman DL, Whitacre JL, Barrows BD, Marroquin LD, Müller R, Brown JR, Hennet T, Esko JD, Aroian RV. Resistance to a bacterial toxin is mediated by removal of a conserved glycosylation pathway required for toxin-host interactions. J Biol Chem 2003; 278:45594-602. [PMID: 12944392 DOI: 10.1074/jbc.m308142200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Crystal (Cry) proteins made by the bacterium Bacillus thuringiensis are pore-forming toxins that specifically target insects and nematodes and are used around the world to kill insect pests. To better understand how pore-forming toxins interact with their host, we have screened for Caenorhabditis elegans mutants that resist Cry protein intoxication. We find that Cry toxin resistance involves the loss of two glycosyltransferase genes, bre-2 and bre-4. These glycosyltransferases function in the intestine to confer susceptibility to toxin. Furthermore, they are required for the interaction of active toxin with intestinal cells, suggesting they make an oligosaccharide receptor for toxin. Similarly, the bre-3 resistance gene is also required for toxin interaction with intestinal cells. Cloning of the bre-3 gene indicates it is the C. elegans homologue of the Drosophila egghead (egh) gene. This identification is striking given that the previously identified bre-5 has homology to Drosophila brainiac (brn) and that egh-brn likely function as consecutive glycosyltransferases in Drosophila epithelial cells. We find that, like in Drosophila, bre-3 and bre-5 act in a single pathway in C. elegans. bre-2 and bre-4 are also part of this pathway, thereby extending it. Consistent with its homology to brn, we demonstrate that C. elegans bre-5 rescues the Drosophila brn mutant and that BRE-5 encodes the dominant UDP-GlcNAc:Man GlcNAc transferase activity in C. elegans. Resistance to Cry toxins has uncovered a four component glycosylation pathway that is functionally conserved between nematodes and insects and that provides the basis of the dominant mechanism of resistance in C. elegans.
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Affiliation(s)
- Joel S Griffitts
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093, USA
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Ramasamy V, Ramakrishnan B, Boeggeman E, Qasba PK. The role of tryptophan 314 in the conformational changes of beta1,4-galactosyltransferase-I. J Mol Biol 2003; 331:1065-76. [PMID: 12927542 DOI: 10.1016/s0022-2836(03)00790-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
beta1,4-Galactosyltransferase-I (beta4Gal-T1) undergoes critical conformational changes upon substrate binding from an open conformation (conf-I) to the closed conformation (conf-II). This change involves two flexible loops: the small (residues 313-316) and the long loop (residues 345-365). Upon substrate binding, Trp314 in the small flexible loop moves towards the catalytic pocket and interacts with the donor and the acceptor substrates. For a better understanding of the role played by Trp314 in the conformational changes of beta4Gal-T1, we mutated it to Ala and carried out substrate-binding, proteolytic and crystallographic studies. The W314A mutation reduces the enzymatic activity, binding to substrates and to the modifier protein, alpha-lactalbumin (LA), by over 99%. The limited proteolysis with Glu-C or Lys-C proteases shows differences in the rate of cleavage of the long loop of the wild-type and mutant W314A, indicating conformational differences in the region between the two proteins. Without substrate, the mutant crystallizes in a conformation (conf-I') (1.9A resolution crystal structure), that is not identical with, but close to an open conformation (conf-I), whereas its complex with the substrates and alpha-lactalbumin, crystallizes in a conformation (2.3A resolution crystal structure) that is identical with the closed conformation (conf-II). This study shows the crucial role Trp314 plays in the conformational state of the long loop, in the binding of substrates and in the catalytic mechanism of the enzyme.
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Affiliation(s)
- Velavan Ramasamy
- Structural Glycobiology Section, LECB, CCR, NCI-Frederick, Building 469, Room 221, 21702, Frederick, MD, USA
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31
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Ramakrishnan B, Qasba PK. Structure-based design of beta 1,4-galactosyltransferase I (beta 4Gal-T1) with equally efficient N-acetylgalactosaminyltransferase activity: point mutation broadens beta 4Gal-T1 donor specificity. J Biol Chem 2002; 277:20833-9. [PMID: 11916963 DOI: 10.1074/jbc.m111183200] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta1,4-Galactosyltransferase I (Gal-T1) normally transfers Gal from UDP-Gal to GlcNAc in the presence of Mn(2+) ion. In the presence of alpha-lactalbumin (LA), the Gal acceptor specificity is altered from GlcNAc to Glc. Gal-T1 also transfers GalNAc from UDP-GalNAc to GlcNAc, but with only approximately 0.1% of Gal-T activity. To understand this low GalNAc-transferase activity, we have carried out the crystal structure analysis of the Gal-T1.LA complex with UDP-GalNAc at 2.1-A resolution. The crystal structure reveals that the UDP-GalNAc binding to Gal-T1 is similar to the binding of UDP-Gal to Gal-T1, except for an additional hydrogen bond formed between the N-acetyl group of GalNAc moiety with the Tyr-289 side chain hydroxyl group. Elimination of this additional hydrogen bond by mutating Tyr-289 residue to Leu, Ile, or Asn enhances the GalNAc-transferase activity. Although all three mutants exhibit enhanced GalNAc-transferase activity, the mutant Y289L exhibits GalNAc-transferase activity that is nearly 100% of its Gal-T activity, even while completely retaining its Gal-T activity. The steady state kinetic analyses on the Leu-289 mutant indicate that the K(m) for GlcNAc has increased compared to the wild type. On the other hand, the catalytic constant (k(cat)) in the Gal-T reaction is comparable with the wild type, whereas it is 3-5-fold higher in the GalNAc-T reaction. Interestingly, in the presence of LA, these mutants also transfer GalNAc to Glc instead of to GlcNAc. The present study demonstrates that, in the Gal-T family, the Tyr-289/Phe-289 residue largely determines the sugar donor specificity.
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Affiliation(s)
- Boopathy Ramakrishnan
- Structural Glycobiology Section and Intramural Research Support Program-SAIC, Laboratory of Experimental and Computational Biology, Center for Cancer Research, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702, USA
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