Determination of the site-specific O-glycosylation pattern of the porcine submaxillary mucin tandem repeat glycopeptide. Model proposed for the polypeptide:galnac transferase peptide binding site.
Determination of the site-specific O-glycosylation pattern of the porcine submaxillary mucin tandem repeat glycopeptide. Model proposed for the polypeptide:galnac transferase peptide binding site.
复制标题
猪颌下粘蛋白串联重复糖肽位点特异性 O-糖基化模式的测定。
DOI：
10.1074/jbc.272.15.9709
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
Pasumarthy,M
中科院分区：
文献类型：
--
作者：
Gerken,TA;Owens,CL;Pasumarthy,M
从猪颌下腺粘蛋白（PSM）中分离出一种糖基化的81位胰蛋白酶串联重复糖肽，并通过氨基酸序列测定确定其糖基化模式。这些研究的关键是能够通过温和的三氟甲磺酸处理将结构异质的PSM寡糖侧链修剪成均质的GalNAc单糖侧链。胰蛋白酶处理三氟甲磺酸处理的PSM释放81个残基的串联重复序列，作为具有不同糖基化模式的81个残基的糖肽的集合。使用重复序列的Edman降解化学的自动氨基酸测序用于确定几乎每个Ser和Thr残基的糖基化程度。Thr残基在73- 90%的范围内全部高度糖基化，得到83%的平均Thr糖基化。相比之下，Ser残基显示出广泛的糖基化，范围在33%和95%之间，得到74%的平均Ser糖基化。这些数据与猪UDP-N-乙酰半乳糖胺：多肽N-乙酰半乳糖胺转移酶的已知Thr肽相对于Ser肽的糖基化升高一致。还观察到重复的糖基化程度与已发表的预测方法相关性很差。糖基化位点周围序列的检查显示，几乎所有高度糖基化的位点都具有倒数第二个Gly残基，而那些不太高度糖基化的位点具有中等至大的侧链倒数第二个残基。如其他人所观察到的，糖基化似乎也受到Pro残基的存在的调节。基于这些发现，我们认为受体肽以β样构象结合转移酶，倒数第二个残基侧链空间相互作用可能在确定给定Ser或Thr糖基化的程度中起作用。GalNAc转移酶肽结合位点的模型提出。
The heterogeneously glycosylated 81-residue tryptic tandem repeat glycopeptide from porcine submaxillary mucin (PSM) has been isolated and its glycosylation pattern determined by amino acid sequencing. Key to these studies is the ability to trim the structurally heterogeneous PSM oligosaccharide side chains to homogeneous GalNAc monosaccharide side chains by mild trifluoromethanesulfonic acid treatment. Trypsin treatment of trifluoromethanesulfonic acid-treated PSM releases the 81-residue tandem repeat as an ensemble of 81-residue glycopeptides with different glycosylation patterns. Automated amino acid sequencing using Edman degradative chemistry of the repeat was used to determine the extent of glycosylation of nearly every Ser and Thr residue. The Thr residues are all highly glycosylated within the range of 73-90%, giving an average Thr glycosylation of 83%. In contrast, the Ser residues display a wide range of glycosylations, ranging between 33 and 95%, giving an average Ser glycosylation of 74%. These data are consistent with the known elevated glycosylation of Thr peptides over Ser peptides for the porcine UDP-N-acetylgalactosamine:polypeptideN-acetylgalactosaminyltransferase. It is also observed that the extent of glycosylation of the repeat correlates poorly with published predictive methods. An examination of the sequences surrounding the glycosylation sites reveals that nearly all of the highly glycosylated sites have a penultimate Gly residue, whereas those that are less highly glycosylated have medium to large side chain penultimate residues. As observed by others, glycosylation also appears to be modulated by the presence of Pro residues. On the basis of these findings we suggest that the acceptor peptide binds the transferase in a β-like conformation and that penultimate residue side chain steric interactions may play a role in determining extent that a given Ser or Thr is glycosylated. A model for the GalNAc transferase peptide binding site is proposed.