Mucin core O-glycosylation is modulated by neighboring residue glycosylation status -: Kinetic modeling of the site-specific glycosylation of the APO-porcine submaxillary mucin tandem repeat by UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases T1 AND T2
Mucin core O-glycosylation is modulated by neighboring residue glycosylation status -: Kinetic modeling of the site-specific glycosylation of the APO-porcine submaxillary mucin tandem repeat by UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases T1 AND T2
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DOI：
10.1074/jbc.m205851200
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发表时间：
2002-12-20
影响因子：
4.8
通讯作者：
Elhammer, Å
中科院分区：
文献类型：
--
作者：
Gerken, TA;Zhang, JX;Elhammer, Å
肽序列和环境对粘蛋白O-糖基化的起始和延伸的影响还不清楚。含有31个O-糖基化位点的猪颌下腺粘蛋白（PSM）串联重复序列的体内糖基化模式（Gerken，T.一、Gilmore，M.，和Zhang，J.（2002）J.Biol.Chem.277，7736-7751）揭示了羟基氨基酸密度（以及由此推断的糖基化密度）与GalNAc糖基化和核心-1取代程度的弱负相关性。我们现在报告的时间过程中，在体外糖基化的apoPSM串联重复的重组UDP-GalNAc：多肽α-GalNAc转移酶（ppGalNAc转移酶）T1和T2证实了这些发现。发现了广泛的糖基化速率，其中几个残基在糖基化中显示出明显的平台。一个可调的动力学模型，减少了一阶速率常数成比例的相邻糖基化状态，加上或减去三个残基的糖基化位点，被发现合理地再现实验速率数据的两种转移酶，包括明显的高原糖基化。独特的，转移酶特异性，位置加权常数揭示了每个转移酶的肽/糖肽识别位点的信息。这两种转移酶显示高灵敏度相邻的Ser/Thr糖基化，而ppGalNAc T2显示额外的高灵敏度的存在下，nonglycosylated Ser/Thr残基。这是第一次证明能够模拟粘蛋白O-糖基化动力学，证实在适当的条件下，邻近的糖基化状态可以是调节粘蛋白O-聚糖生物合成的第一步的重要因素。
The influence of peptide sequence and environment on the initiation and elongation of mucin O-glycosylation is not well understood. The in vivo glycosylation pattern of the porcine submaxillary gland mucin (PSM) tandem repeat containing 31 O-glycosylation sites (Gerken, T. A., Gilmore, M., and Zhang, J. (2002) J. Biol. Chem. 277, 7736-7751) reveals a weak inverse correlation with hydroxyamino acid density (and by inference the density of glycosylation) with the extent of GalNAc glycosylation and core-1 substitution. We now report the time course of the in vitro glycosylation of the apoPSM tandem repeat by recombinant UDP-GalNAc:polypeptide alpha-GalNAc transferases (ppGalNAc transferase) T1 and T2 that confirm these findings. A wide range of glycosylation rates are found, with several residues showing apparent plateaus in glycosylation. An adjustable kinetic model that reduces the first-order rate constants proportional to neighboring glycosylation status, plus or minus three residues of the site of glycosylation, was found to reasonably reproduce the experimental rate data for both transferases, including apparent plateaus in glycosylation. The unique, transferase-specific, positional weighting constants reveal information on the peptide/glycopeptide recognition site for each transferase. Both transferases displayed high sensitivities to neighboring Ser/Thr glycosylation, whereas ppGalNAc T2 displayed additional high sensitivities to the presence of nonglycosylated Ser/Thr residues. This is the first demonstration of the ability to model mucin O-glycosylation kinetics, confirming that under the appropriate conditions neighboring glycosylation status can be a significant factor modulating the first step of mucin O-glycan biosynthesis.