Saeki Yasushi, Tayama Yoko, Toh-e Akio, Yokosawa Hideyoshi
Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Biochem Biophys Res Commun. 2004 Jul 30;320(3):840-5. doi: 10.1016/j.bbrc.2004.05.216.
Saccharomyces cerevisiae Ufd2 is a ubiquitin chain elongation factor in the ubiquitin fusion degradation (UFD) pathway and functions in stress tolerance. A recent study has suggested that the mammalian Ufd2 homologue UFD2a catalyzes formation of Lys27- and Lys33-linked polyubiquitin chains rather than the Lys48-linked chain, but the linkage type of the polyubiquitin chain formed by yeast Ufd2 remains unclear. To determine the property of Ufd2, we reconstituted the UFD pathway using purified enzymes from yeast. Direct determination of the ubiquitin chain linkage type in polyubiquitinated UFD substrates by MALDI-TOF mass spectrometry revealed that Ufd2 catalyzes elongation of the ubiquitin chain through Lys48 linkage.
酿酒酵母Ufd2是泛素融合降解（UFD）途径中的泛素链延伸因子，在应激耐受中发挥作用。最近的一项研究表明，哺乳动物Ufd2同源物UFD2a催化形成赖氨酸27和赖氨酸33连接的多聚泛素链，而不是赖氨酸48连接的链，但酵母Ufd2形成的多聚泛素链的连接类型仍不清楚。为了确定Ufd2的特性，我们使用从酵母中纯化的酶重建了UFD途径。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF质谱）直接测定多聚泛素化UFD底物中的泛素链连接类型，结果表明Ufd2通过赖氨酸48连接催化泛素链的延伸。
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