The yeast vacuolar Rab GTPase Ypt7p has an activity beyond membrane recruitment of the homotypic fusion and protein sorting-Class C Vps complex.
The yeast vacuolar Rab GTPase Ypt7p has an activity beyond membrane recruitment of the homotypic fusion and protein sorting-Class C Vps complex.
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酵母液泡 Rab GTP 酶 Ypt7p 的活性超出了同型融合和蛋白质分选 C 类 Vps 复合物的膜招募范围。
DOI：
10.1042/bj20110687
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Stroupe,Christopher
中科院分区：
文献类型：
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作者：
Stroupe,Christopher
先前的一份报告描述了用脂质混合物模拟酵母液泡组成的重组蛋白脂质体的脂质混合。这种脂质混合需要SNARE {SNAP[可溶性NSF （n -乙基丙烯酰亚胺敏感因子）-粘附蛋白]受体}蛋白、Sec18p和Sec17p（酵母NSF和α-SNAP）和HOPS（同型融合和蛋白分选）- C类Vps（液泡蛋白分选）复合物，但不需要液泡Rab GTPase Ypt7p。本研究探讨了Ypt7p在蛋白脂质体脂质混合中的活性。缺少心磷脂的蛋白脂质体[1,3-二-（sn-3′-磷脂酰）-sn-甘油]的脂质混合需要Ypt7p。遗漏其他带负电荷和/或小头基团的脂质不会导致Ypt7p对脂质混合的依赖。由CRD1（心磷脂合成酶）破坏的菌株制成的酵母液泡与具有功能CRD1的菌株的液泡融合程度相同。CRD1的破坏不会改变液泡融合对Rab gtpase的依赖。有人提出，将啤酒花复合物募集到膜上是Ypt7p的主要功能。然而，即使在混合脂质反应中调整了HOPS复合物的浓度，使无心磷脂的蛋白脂质体与含有或不含有Ypt7p的相同数量的HOPS结合，Ypt7p仍然是脂质混合所必需的。因此，Ypt7p必须通过一种机制来刺激膜融合，这种机制除了向膜募集啤酒花之外。这是第一次对Rab GTPase的这种刺激活动的证明，也就是说，超出了主体效应的招募。
A previous report described lipid mixing of reconstituted proteoliposomes made using lipid mixtures that mimic the composition of yeast vacuoles. This lipid mixing required SNARE {SNAP [soluble NSF (N-ethylmaleimide-sensitive factor)-attachment protein] receptor} proteins, Sec18p and Sec17p (yeast NSF and α-SNAP) and the HOPS (homotypic fusion and protein sorting)–Class C Vps (vacuole protein sorting) complex, but not the vacuolar Rab GTPase Ypt7p. The present study investigates the activity of Ypt7p in proteoliposome lipid mixing. Ypt7p is required for the lipid mixing of proteoliposomes lacking cardiolipin [1,3-bis-(sn-3′-phosphatidyl)-sn-glycerol]. Omission of other lipids with negatively charged and/or small head groups does not cause Ypt7p dependence for lipid mixing. Yeast vacuoles made from strains disrupted for CRD1 (cardiolipin synthase) fuse to the same extent as vacuoles from strains with functional CRD1. Disruption of CRD1 does not alter dependence on Rab GTPases for vacuole fusion. It has been proposed that the recruitment of the HOPS complex to membranes is the main function of Ypt7p. However, Ypt7p is still required for lipid mixing even when the concentration of HOPS complex in lipid-mixing reactions is adjusted such that cardiolipin-free proteoliposomes with or without Ypt7p bind to equal amounts of HOPS. Ypt7p therefore must stimulate membrane fusion by a mechanism that is in addition to recruitment of HOPS to the membrane. This is the first demonstration of such a stimulatory activity–that is, beyond bulk effector recruitment–for a Rab GTPase.