Asparagine-linked glycosylation is an essential and highly conserved protein modification reaction that occurs in the endoplasmic reticulum of cells during protein synthesis at the ribosome. In the central reaction, a pre-assembled high-mannose sugar is transferred from a lipid-linked donor substrate to the side-chain of an asparagine residue in an –N–X–T/S– sequence (where X is any residue except proline). This reaction is carried by a membrane-bound multi-subunit enzyme complex, oligosaccharyltransferase (OST). In humans, genetic defects in OST lead to a group of rare metabolic diseases collectively known as Congenital Disorders of Glycosylation. Certain mutations are lethal for all organisms. In yeast, the OST is composed of nine non-identical protein subunits. The functional enzyme complex contains eight subunits with either Ost3 or Ost6 at any given time. Ost4, an unusually small protein, plays a very important role in the stabilization of the OST complex. It bridges the catalytic subunit Stt3 with Ost3 (or Ost6) in the Stt3–Ost4–Ost3 (or Ost6) sub-complex. Mutation of any residue from M18-I24 in the trans-membrane helix of yeast Ost4 negatively impacts N-linked glycosylation and the growth of yeast. Indeed, mutation of valine23 to an aspartate impairs OST function in vivo resulting in a lethal phenotype in yeast. To understand the structural mechanism of Ost4 in the stabilization of the enzyme complex, we have initiated a detailed investigation of Ost4 and its functionally important mutant, Ost4V23D. Here, we report the backbone ¹H, ¹³C, and ¹⁵N resonance assignments for Ost4 and Ost4V23D in dodecylphosphocholine micelles.

中文翻译：

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酵母寡糖基转移酶亚基 Ost4 及其功能重要的突变体 Ost4V23D 的 1H、13C、15N 共振分配和二级结构。

天冬酰胺连接的糖基化是一种重要且高度保守的蛋白质修饰反应，在核糖体合成蛋白质期间发生在细胞的内质网中。在中心反应中，预组装的高甘露糖从脂质连接的供体底物转移到 -N-X-T/S- 序列中天冬酰胺残基的侧链（其中 X 是任何残基，除了脯氨酸）。该反应由膜结合的多亚基酶复合物寡糖基转移酶 (OST) 进行。在人类中，OST 的遗传缺陷会导致一组罕见的代谢疾病，统称为先天性糖基化疾病。某些突变对所有生物都是致命的。在酵母中，OST 由九个不同的蛋白质亚基组成。在任何给定时间，功能性酶复合物包含八个带有 Ost3 或 Ost6 的亚基。Ost4 是一种异常小的蛋白质，在稳定 OST 复合物方面起着非常重要的作用。它将催化亚基 Stt3 与 Stt3–Ost4–Ost3（或 Ost6）子复合物中的 Ost3（或 Ost6）桥接起来。酵母 Ost4 跨膜螺旋中来自 M18-I24 的任何残基的突变都会产生负面影响N-连接的糖基化和酵母的生长。事实上，缬氨酸 23 突变为天冬氨酸会损害体内 OST 功能，导致酵母中的致死表型。为了了解 Ost4 稳定酶复合物的结构机制，我们开始了对 Ost4 及其重要功能突变体 Ost4V23D 的详细研究。在这里，我们报告了十二烷基磷酸胆碱胶束中 Ost4 和 Ost4V23D的骨架¹ H、¹³ C 和¹⁵ N 共振分配。