The relationship between ST6Gal I Golgi retention and its cleavage-secretion.
The relationship between ST6Gal I Golgi retention and its cleavage-secretion.
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ST6Gal I 高尔基体保留与其裂解分泌之间的关系。
DOI：
10.1093/oxfordjournals.glycob.a018856
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发表时间：
1999
期刊：
影响因子：
4.3
通讯作者：
Colley,KJ
中科院分区：
文献类型：
--
作者：
Kitazume-Kawaguchi,S;Dohmae,N;Takio,K;Tsuji,S;Colley,KJ
ST 6 Gal I是修饰糖蛋白的N-连接寡糖的唾液酸转移酶。先前的结果表明，管腔干和活性结构域序列的ST 6 Gal I高尔基体保留的效率中的作用。一系列STtyr同种型缺失突变体的表征表明，茎对蛋白酶敏感，并且防止该区域中的切割导致细胞表面表达增加。缺乏氨基酸32-104（STΔ4）的突变体不像野生型STtyr那样具有活性或切割和分泌，但确实表现出增加的细胞表面表达。很可能STΔ4突变体缺乏活性结构域的茎区和一些氨基酸，因为缺乏氨基酸86-104的STΔ5突变体也没有活性，但被切割和分泌。相比之下，STΔ1、STΔ2和STΔ3突变体中残基32和86之间的茎氨基酸的缺失不会使这些酶形式失活，消除它们的切割和分泌，或增加它们的细胞表面表达。令人惊讶的是，即使先前鉴定的Asn 63-Ser 64切割位点缺失，也发生切割。进一步的评价表明，在COS细胞中使用了Lys 40和Glu 41之间的切割位点。赖氨酸40的突变显著降低，但没有消除切割，这表明在ST 6 Gal I茎中存在额外的次级切割位点。
The ST6Gal I is a sialyltransferase that modifies N-linked oligosaccharides of glycoproteins. Previous results suggested a role for luminal stem and active domain sequences in the efficiency of ST6Gal I Golgi retention. Characterization of a series of STtyr isoform deletion mutants demonstrated that the stem is sensitive to proteases and that preventing cleavage in this region leads to increased cell surface expression. A mutant lacking amino acids 32–104 (STΔ4) is not active or cleaved and secreted like the wild type STtyr, but does exhibit increased cell surface expression. It is probable that the STΔ4 mutant lacks the stem region and some amino acids of the active domain because the STΔ5 mutant lacking amino acids 86–104 is also not active but is cleaved and secreted. In contrast, deletion of stem amino acids between residues 32 and 86 in the STΔ1, STΔ2, and STΔ3 mutants does not inactive these enzyme forms, eliminate their cleavage and secretion, or increase their cell surface expression. Surprisingly, cleavage occurs even though the previously identified Asn63-Ser 64 cleavage site is missing. Further evaluation demonstrated that a cleavage site between Lys 40 and Glu 41 is used in COS cells. Mutagenesis of Lys 40 significantly decreased, but did not eliminate cleavage, suggesting that there are additional secondary sites of cleavage in the ST6Gal I stem.