Crystal Structure of the C-Terminal Globular Domain of Oligosaccharyltransferase from Archaeoglobus fulgidus at 1.75 Å Resolution
Crystal Structure of the C-Terminal Globular Domain of Oligosaccharyltransferase from Archaeoglobus fulgidus at 1.75 Å Resolution
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DOI：
10.1021/bi300076u
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发表时间：
2012-05-22
期刊：
影响因子：
2.9
通讯作者：
Kohda, Daisuke
中科院分区：
文献类型：
--
作者：
Matsumoto, Shunsuke;Igura, Mayumi;Kohda, Daisuke
蛋白质N-糖基化存在于生命的三个领域。寡糖转移酶(OST)在N-糖基化序列中将多糖转移到天冬酰胺。OST的催化亚基在真核生物中称为STT3，在古生物中称为AglB，在真细菌中称为PglB。一种极端嗜热的古生物，Archaeoglobus fulgidus的基因组编码了三个AglB Paralog。其中两个是生活中所有领域中最短的Aglb。我们测定了最小AglB的C-末端球状结构域的晶体结构，以确定最小结构单元。Archaeoglobus AglB缺乏在其他AglB和PglB结构中发现的贝塔桶状结构。一致认为，较大的热球菌AglB中的缺失证实了它对活性的可有可无。相比之下，Archaeoglobus AglB包含一个扭曲的螺旋，带有一个保守的基序，称为DK/MI基序。基序中的赖氨酸和异亮氨酸残基参与了Ser/Thr在亮子中的识别。Archaeoglobus AglB的结构显示，扭曲的螺旋包含一个意想不到的插入。基于这一发现的修订序列比对发现了带有插入的DK基序的一种变异类型。对Archaeoglobus AglB的诱变研究证实了这种特殊类型的DK基序对活性的贡献。结合我们以前的研究结果，本研究确定了OST的分类：一组由真核生物和大多数古菌组成的DK型Ser/Thr口袋，另一组由真细菌和其余古菌组成的MI型Ser/Thr口袋。这一分类为OST研究提供了一个有用的框架。
Protein N-glycosylation occurs in the three domains of life. Oligosaccharyltransferase (OST) transfers glycan to asparagine in the N-glycosylation sequon. The catalytic subunit of OST is called STT3 in eukaryotes, AglB in archaea, and PglB in eubacteria. The genome of a hyperthermophilic archaeon, Archaeoglobus fulgidus, encodes three AglB paralogs. Two of them are the shortest AglBs across all domains of life. We determined the crystal structure of the C-terminal globular domain of the smallest AglB to identify the minimal structural unit. The Archaeoglobus AglB lacked a beta-barrel-like structure, which had been found in other AglB and PglB structures. In agreement, the deletion in a larger Pyrococcus AglB confirmed its dispensability for the activity. By contrast, the Archaeoglobus AglB contains a kinked helix bearing a conserved motif, called DK/MI motif. The lysine and isoleucine residues in the motif participate in the Ser/Thr recognition in the sequon. The Archaeoglobus AglB structure revealed that the kinked helix contained an unexpected insertion. A revised sequence alignment based on this finding identified a variant type of the DK motif with the insertion. A mutagenesis study of the Archaeoglobus AglB confirmed the contribution of this particular type of the DK motif to the activity. When taken together with our previous results, this study defined the classification of OST: one group consisting of eukaryotes and most archaea possesses the DK-type Ser/Thr pocket, and the other group consisting of eubacteria and the remaining archaea possesses the MI-type Ser/Thr pocket. This classification provides a useful framework for OST studies.