Site directed processing: Role of amino acid sequences and glycosylation of acceptor glycopeptides in the assembly of extended mucin type O-glycan core 2
Site directed processing: Role of amino acid sequences and glycosylation of acceptor glycopeptides in the assembly of extended mucin type O-glycan core 2
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DOI：
10.1016/j.bbagen.2009.05.020
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发表时间：
2009-10-01
影响因子：
3
通讯作者：
Paulsen, Hans
中科院分区：
文献类型：
--
作者：
Brockhausen, Inka;Dowler, Thomas;Paulsen, Hans
工作背景：具有核心2结构的粘蛋白的Ser/Thr连接的O-聚糖的组装由多肽GalNAc-转移酶（ppGalNAc-T）引发，随后是核心1 β 3-Gal-transferase（C1 GalT）和核心2 β 6-GlcNAc-转移酶（C2 GnT）的作用。β 4-半乳糖转移酶（β 4GalT）延伸核心2并形成生物学重要表位的骨架结构。在慢性疾病中，O-聚糖结构通常是异常的。本工作的目的是确定这些酶的活性和特异性是否受底物的序列和糖基化的指导。方法：我们研究了四种合成扩展的O-聚糖核心2的酶的特异性，所述酶使用合成的粘蛋白衍生肽和糖肽作为受体底物，用GalNAc或O-聚糖核心结构1、2、3、4和6取代。发现特定的Thr残基是添加GalNAc的优选位点，并且发现+3位的Pro特别增强初级糖基化。发现相邻聚糖的大小与GalNAc添加速率之间存在反比关系。所有四种酶都可以区分具有不同氨基酸序列和O-糖基化位点的底物。短糖肽Gal β 1-3GalNAc α-TAGV被鉴定为有效的C2 GnT底物。结论：组装扩展核心2结构的四种酶的活性受受体糖肽中氨基酸序列和附近残基上糖的存在的影响。特别是，序列和O-糖基化模式直接添加的第一个和第二个糖残基的ppGalNAc-T和C1 GalT，其作用在一个站点定向fashion.General意义：知识的站点定向加工增强了我们的理解的控制O-糖基化在正常细胞和疾病。(C)2009 Elsevier B. V.保留所有权利。
Background: The assembly of Ser/Thr-linked O-glycans of mucins with core 2 structures is initiated by polypeptide GalNAc-transferase (ppGalNAc-T), followed by the action of core 1 beta 3-Gal-transferase (C1GalT) and core 2 beta 6-GlcNAc-transferase (C2GnT). beta 4-Gal-transferase (beta 4GalT) extends core 2 and forms the backbone structure for biologically important epitopes. O-glycan structures are often abnormal in chronic diseases. The goal of this work is to determine if the activity and specificity of these enzymes are directed by the sequences and glycosylation of substrates.Methods: We studied the specificities of four enzymes that synthesize extended O-glycan core 2 using as acceptor substrates synthetic mucin derived peptides and glycopeptides, substituted with GalNAc or O-glycan core structures 1, 2, 3, 4 and 6.Results: Specific Thr residues were found to be prefer-red sites for the addition of GalNAc, and Pro in the + 3 position was found to especially enhance primary glycosylation. An inverse relationship was found between the size of adjacent glycans and the rate of GalNAc addition. All four enzymes could distinguish between substrates having different amino acid sequences and O-glycosylated sites. A short glycopeptide Gal beta 1-3GalNAc alpha-TAGV was identified as an efficient C2GnT substrate.Conclusions: The activities of four enzymes assembling the extended core 2 structure are affected by the amino acid sequence and presence of carbohydrates on nearby residues in acceptor glycopeptides. In particular, the sequences and O-glycosylation patterns direct the addition of the first and second sugar residues by ppGalNAc-T and C1GalT which act in a site directed fashion.General significance: Knowledge of site directed processing enhances our understanding of the control of O-glycosylation in normal cells and in disease. (C) 2009 Elsevier B.V. All rights reserved.