Taylor Sean C, Ferguson Andrew D, Bergeron John J M, Thomas David Y
Biochemistry Department, Faculty of Medicine, McGill University, McIntyre Medical Sciences Building, 3655 Boulevard Sir William Osler, Montreal, Quebec, Canada, H3G 1Y6.
Nat Struct Mol Biol. 2004 Feb;11(2):128-34. doi: 10.1038/nsmb715. Epub 2004 Jan 4.
We present in vitro data that explain the recognition mechanism of misfolded glycoproteins by UDP-glucose glycoprotein-glucosyltransferase (UGGT). The glycoprotein exo-(1,3)-beta-glucanase (beta-Glc) bearing two glycans unfolds in a pH-dependent manner to become a misfolded substrate for UGGT. In the crystal structure of this glycoprotein, the local hydrophobicity surrounding each glycosylation site coincides with the differential recognition of N-linked glycans by UGGT. We introduced a single F280S point mutation, producing a beta-Glc protein with full enzymatic activity that was both recognized as misfolded and monoglucosylated by UGGT. Contrary to current views, these data show that UGGT can modify N-linked glycans positioned at least 40 A from localized regions of disorder and sense subtle conformational changes within structurally compact, enzymatically active glycoprotein substrates.
我们展示了体外数据，这些数据解释了UDP-葡萄糖糖蛋白葡糖基转移酶（UGGT）对错误折叠糖蛋白的识别机制。带有两个聚糖的糖蛋白外切（1,3）-β-葡聚糖酶（β-Glc）以pH依赖的方式展开，成为UGGT的错误折叠底物。在这种糖蛋白的晶体结构中，每个糖基化位点周围的局部疏水性与UGGT对N-连接聚糖的差异识别相一致。我们引入了一个单一的F280S点突变，产生了一种具有完全酶活性的β-Glc蛋白，该蛋白被UGGT识别为错误折叠并进行了单葡糖基化。与当前观点相反，这些数据表明UGGT可以修饰位于距局部无序区域至少40埃处的N-连接聚糖，并感知结构紧凑、具有酶活性的糖蛋白底物内的细微构象变化。
