Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD 20910, USA.
Mol Microbiol. 2011 Sep;81(5):1133-5. doi: 10.1111/j.1365-2958.2011.07782.x. Epub 2011 Aug 16.
N-linked protein glycosylation occurs in all three branches of life, eukaryotes, bacteria and archaea. The simplest system is that of the bacterium, Campylobacter jejuni, in which a heptasaccharide glycan is added to multiple proteins from a single lipid carrier molecule. In the eukaryotic system a conserved tetradecasaccharide modification is first added to target proteins, but is then modified by trimming and addition of other glycans from additional carrier molecules resulting in a diverse array of glycans of distinct functionality. In the halophilic Archaea from the Dead Sea, Haloferax volcanii, the surface array or S-layer protein is glycosylated with a pentasaccharide. This glycan is synthesized from two separate carrier molecules, one that carries a tetrasaccharide and another that carries the terminal mannose, in a process that is analogous to that of eukaryotes. In this issue of Molecular Microbiology the glycosylation of the S-layer of another halophilic Archaea from the Dead Sea, Haloarcula marismortui is characterized (Calo et al., 2011). This S-layer is glycosylated with the same pentasaccharide as that of Hfx. volcanii, but the intact pentasaccharide is synthesized on a single carrier molecule in Har. marismortui in a process that more closely resembles that of the bacterial N-linked system.
N-连接蛋白糖基化发生在所有三个生命领域，真核生物、细菌和古菌。最简单的系统是弯曲杆菌的系统，其中七糖聚糖被添加到来自单个脂质载体分子的多种蛋白质中。在真核系统中，首先将保守的十四聚糖修饰添加到靶蛋白上，但随后通过修剪和从其他载体分子添加其他聚糖进行修饰，导致具有不同功能的各种聚糖。在死海中的嗜盐古菌 Haloferax volcanii 中，表面阵列或 S-层蛋白与五糖聚糖糖基化。该聚糖由两个独立的载体分子合成，一个载体携带四糖，另一个载体携带末端甘露糖，其过程类似于真核生物。在本期《分子微生物学》中，对来自死海的另一种嗜盐古菌 Haloarcula marismortui 的 S-层糖基化进行了描述（Calo 等人，2011）。该 S-层与 Hfx 的五糖聚糖糖基化。火山，但完整的五糖聚糖在 Har 上的单个载体分子上合成。在 marismortui 中，该过程更类似于细菌 N-连接系统。
