Kim Young-Cheon, Hartweck Lynn M, Olszewski Neil E
The Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN, United States.
Front Plant Sci. 2024 Jul 18;15:1343066. doi: 10.3389/fpls.2024.1343066. eCollection 2024.
The glycosyl transferases SPINDLY (SPY) and SECRET AGENT (SEC) modify nuclear and cytosolic proteins with -linked fucose or -linked -acetylglucosamine (-GlcNAc), respectively. -fucose and -GlcNAc modifications can occur at the same sites. SPY interacts physically and genetically with GIGANTEA (GI), suggesting that it could be modified by both enzymes. Previously, we found that, when co-expressed in , SEC modifies GI; however, the modification site was not determined. By analyzing the overlapping sub-fragments of GI, we identified a region that was modified by SEC in . Modification was undetectable when threonine 829 (T829) was mutated to alanine, while the T834A and T837A mutations reduced the modification, suggesting that T829 was the primary or the only modification site. Mapping using mass spectrometry detected only the modification of T829. Previous studies have shown that the positions modified by SEC in are modified , suggesting that T829 is -GlcNAc modified .
糖基转移酶SPINDLY（SPY）和SECRET AGENT（SEC）分别用α-连接的岩藻糖或β-连接的N-乙酰葡糖胺（β-GlcNAc）修饰核蛋白和胞质蛋白。α-岩藻糖基化和β-GlcNAc修饰可发生在相同位点。SPY在物理和遗传上与GIGANTEA（GI）相互作用，这表明它可能被这两种酶修饰。此前，我们发现，当在酵母中共表达时，SEC修饰GI；然而，修饰位点尚未确定。通过分析GI的重叠亚片段，我们确定了一个在酵母中被SEC修饰的区域。当苏氨酸829（T829）突变为丙氨酸时，未检测到修饰，而T834A和T837A突变减少了修饰，这表明T829是主要或唯一的修饰位点。使用质谱进行的定位仅检测到T829的修饰。先前的研究表明，在酵母中被SEC修饰的位点在植物中也被修饰，这表明T829被β-GlcNAc修饰。
