- Characterization of the single-subunit oligosaccharyltransferase STT3A from Trypanosoma brucei using synthetic peptides and lipid-linked oligosaccharide analogs
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The initial transfer of a complex glycan in protein N-glycosylation is catalyzed by oligosaccharyltransferase (OST), which is generally a multisubunit membrane protein complex in the endoplasmic reticulum but a single-subunit enzyme (ssOST) in some protists. To investigate the reaction mechanism of ssOST, we recombinantly expressed, purified and characterized the STT3A protein from Trypanosoma brucei (TbSTT3A). We analyzed the in vitro activity of TbSTT3A by synthesizing fluorescently labeled acceptor peptides as well as lipid-linked oligosaccharide (LLO) analogs containing a chitobiose moiety coupled to oligoprenyl carriers of distinct lengths (C10, C15, C20 and C25) and with different double bond stereochemistry. We found that in addition to proline, charged residues at the +1 position of the sequon inhibited glycan transfer. An acidic residue at the -2 position significantly increased catalytic turnover but was not essential, in contrast to the bacterial OST. While all synthetic LLO analogs were processed by TbSTT3A, the length of the polyprenyl tail, but not the stereochemistry of the double bonds, determined their apparent affinity. We also synthesized phosphonate analogs of the LLOs, which were found to be competitive inhibitors of the reaction, although with lower apparent affinity to TbSTT3A than the active pyrophosphate analogs.
- Ramírez, Ana S.,Boilevin, Jérémy,Biswas, Rasomoy,Gan, Bee Ha,Janser, Daniel,Aebi, Markus,Darbre, Tamis,Reymond, Jean-Louis,Locher, Kaspar P.
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p. 525 - 535
(2017/06/09)
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- N-GLYCOSYLATION OF PEPTIDES AND PROTEINS
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A process for the production of a glycoconjugate by N-glycosylation of a protein or peptide comprising the sequence D/E-X-N-X-S/T, wherein each X is the same or different and is any natural amino acid other than proline, wherein the process comprises reacting the protein or peptide with a polyisoprenyl pyrophosphate of formula (I), or a salt thereof, in the presence of PglB: (I) to produce the glycoconjugate comprising the protein or peptide having a saccharide [SI] linked to the asparagine in the sequence D/E-X-N-X-S/T. Polyisoprenylpyrophosphates used as substrates in the biocatalytic process are also provided, as well as certain glycoconjugates.
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Page/Page column 16; 17
(2015/05/05)
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- Rationally designed short polyisoprenol-linked PglB substrates for engineered polypeptide and protein N-glycosylation
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The lipid carrier specificity of the protein N-glycosylation enzyme C. jejuni PglB was tested using a logical, synthetic array of natural and unnatural C10, C20, C30, and C40 polyisoprenol sugar pyrophosphates, including those bearing repeating cis-prenyl units. Unusual, short, synthetically accessible C20 prenols (nerylnerol 1d and geranylnerol 1e) were shown to be effective lipid carriers for PglB sugar substrates. Kinetic analyses for PglB revealed clear KM-only modulation with lipid chain length, thereby implicating successful in vitro application at appropriate concentrations. This was confirmed by optimized, efficient in vitro synthesis allowing >90% of Asn-linked β-N-GlcNAc-ylated peptide and proteins. This reveals a simple, flexible biocatalytic method for glycoconjugate synthesis using PglB N-glycosylation machinery and varied chemically synthesized glycosylation donor precursors.
- Liu, Feng,Vijayakrishnan, Balakumar,Faridmoayer, Amirreza,Taylor, Thomas A.,Parsons, Thomas B.,Bernardes, Goncalo J.L.,Kowarik, Michael,Davis, Benjamin G.
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supporting information
p. 566 - 569
(2014/02/14)
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- Gold-catalyzed cyclization of oxo-1,5-enynes
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Cationic gold(I) complexes catalyze the cycloisomerization of oxo-1,5-enynes to form oxatricyclic derivatives through an intramolecular Prins reaction. Georg Thieme Verlag Stuttgart. New York.
- Huguet, Núria,Echavarren, Antonio M.
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supporting information; experimental part
p. 49 - 53
(2012/02/14)
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- Selective C - S bond formation via Fe-catalyzed allylic substitution
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In contrast to the formation of C - O and C - N bonds it was only recently that the selective C - S bond formation by means of transition metal complexes moved more into the center of research. This is somewhat surprising given the fact that the sulfur at
- Jegelka, Markus,Plietker, Bernd
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supporting information; experimental part
p. 3462 - 3465
(2009/12/05)
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- Superacidic low temperature cyclization of terpenylphenyisulfones
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The superacidic cyclization of aliphatic and partially cyclized C10- C20 terpenylphenylsulfones proceeds structure-selectively and stereospecifically, affording α- or mixtures of α- and γ-isomers of completely cyclized terpenylphenylsulfones. The configuration of the phenylsuffonylmethylene group in the cyclized products is predetermined by the configuration of the allylic double bond in the starting compounds.
- Kulcitki, Veaceslav,Ungur, Nicon,Vlad, Pavel F.
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p. 11925 - 11934
(2007/10/03)
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- Regioselective Preparation of Allylic Sulfones by Palladium-Catalyzed Reactions of Allylic Nitro Compounds with Sodium Benzenesulfinate
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Treatment of allylic nitro compounds with sodium benzenesulfinate in the presence of 5 molpercent of Pd(PPh3)4 in N,N-dimethylformamide (DMF) at 20-70 deg C for 1-10 h resulted in the formation of allylic sulfones with predominance of kinetically controll
- Ono, Noboru,Hamamoto, Isami,Kawai, Takashi,Kaji, Aritsune,Tamura, Rui,Kakihana, Masato
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p. 405 - 410
(2007/10/02)
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- A New Synthesis of Olefins via the Elimination Reaction of β-Tributylstannyl Organosulfur Compounds
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Organosulfur compounds on treatment with butyllithium in tetrahydrofuran followed by tributylstannylmethyl iodide 1 afforded olefins.The reaction was found to proceed via the destannylsulfurization of the initially formed β-stannyl organosulfur compounds.Thus, allyl 2-pyridyl sulfides 2 or allyl phenyl sulfones 12 were converted into 1,3-dienes 4.Compounds 13 and 15 were converted into the olefins 14 and 17.Furthermore, the reaction was applied to the synthesis of α-substituted vinyl sulfides 24 and allene 27.The stereochemistry of the double bond is discussed.Keywords - destannylsulfurization; allyl 2-pyridyl sulfide; allyl phenyl sulfone; synthesis of olefin; 1,3-diene; vinyl sulfide; β-tributylstannyl organosulfur compound.
- Ochiai, Masahito,Ukita, Tatsuzo,Fujita, Eiichi,Tada, Shin-ichi
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p. 1829 - 1839
(2007/10/02)
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- SYNTHESIS OF TRANS-4,8,12,15,15-PENTAMETHYLBICYCLOPENTADECA-3E,7Z,12Z-TRIENE, A GEOMETRICAL ISOMER OF ANHYDROVERTICILLOL
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A 7Z-isomer of anhydroverticillol skeleton was constructed in 15 percent yield when the 7E allyl bromide having secoverticillol framework was treated with LiN(TMS)2.Reductive removal of the SO2Ph group furnished a geometrical isomer of anhydroverticillol.
- Kumagai, Takashi,Ise, Fumiaki,Uyehara, Tadao,Kato, Tadahiro
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- Stereoselective Synthesis of (+/-)-Irones
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β-, α-cis-, and α-trans-irones (1, 2a, and 2b) have been prepared via 2,5,6,6-tetramethyl-1-cyclohexene (7) and 1,4β,5,5-tetramethyl-6β-cyclohexene (8a) and its C-6 epimer (8b).Electrochemical epoxidation of
- Torii, Sigeru,Uneyama, Kenji,Matsunami, Setsuo
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