Characterization of the single-subunit oligosaccharyltransferase STT3A from Trypanosoma brucei using synthetic peptides and lipid-linked oligosaccharide analogs
作者:Ana S Ramírez、Jérémy Boilevin、Rasomoy Biswas、Bee Ha Gan、Daniel Janser、Markus Aebi、Tamis Darbre、Jean-Louis Reymond、Kaspar P Locher
DOI:10.1093/glycob/cwx017
日期:2017.6
well as lipid-linked oligosaccharide (LLO) analogs containing a chitobiose moiety coupled to oligoprenyl carriers of distinct lengths (C10, C15, C20 and C25) and with different double bond stereochemistry. We found that in addition to proline, charged residues at the +1 position of the sequon inhibited glycan transfer. An acidic residue at the -2 position significantly increased catalytic turnover but
复合糖聚糖在蛋白质N-糖基化中的初始转移是由寡糖基转移酶(OST)催化的,寡糖基转移酶通常是内质网中的多亚基膜蛋白复合物,但在某些原生生物中是单亚基酶(ssOST)。为了研究ssOST的反应机理,我们重组表达,纯化和鉴定了布鲁氏锥虫(TbSTT3A)的STT3A蛋白。我们通过合成荧光标记的受体肽以及脂质连接的寡糖(LLO)类似物来分析TbSTT3A的体外活性,该类似物包含与不同长度(C10,C15,C20和C25)的异戊二烯基载体偶联的壳二糖部分立体化学。我们发现,除脯氨酸外,子序列+1位的带电荷残基还抑制了聚糖的转移。与细菌OST相反,在-2位置的酸性残基显着增加了催化转化率,但不是必需的。尽管所有合成的LLO类似物均由TbSTT3A处理,但聚异戊二烯尾部的长度(而不是双键的立体化学)决定了它们的表观亲和力。我们还合成了LLO的膦酸酯类似物,虽然与活性焦磷酸盐类似物相比,其对TbSTT3