Genetic interactions in yeast between Ypt GTPases and Arf guanine nucleotide exchangers.
Genetic interactions in yeast between Ypt GTPases and Arf guanine nucleotide exchangers.
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酵母中 Ypt GTPases 和 Arf 鸟嘌呤核苷酸交换器之间的遗传相互作用。
DOI：
10.1093/genetics/152.4.1543
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发表时间：
1999
期刊：
影响因子：
3.3
通讯作者：
Segev,N
中科院分区：
文献类型：
--
作者：
Jones,S;Jedd,G;Kahn,RA;Franzusoff,A;Bartolini,F;Segev,N
GTP酶的两个家族Arfs和Ypt/rabs是囊泡运输的关键调节因子。虽然Arf蛋白参与囊泡从供体隔室出芽，但Ypt/rab蛋白参与囊泡向受体隔室的靶向。最近，我们已经显示了Ypt 31/32 p在退出酵母trans-Golgi中的作用，这表明Ypt/rab蛋白在囊泡出芽中也可能具有功能。在这里，我们报告的Sec 7-域家族，SYT 1，作为一个高拷贝的ypt 31/32突变的抑制剂的新成员的鉴定。几种属于Sec 7结构域家族的蛋白质，包括酵母Gea 1 p，最近已被证明可以刺激Arf GTP酶的核苷酸交换。Arf GTP酶的核苷酸交换，即从GDP结合形式到GTP结合形式的转换，被认为对其功能至关重要。Sec 7 p本身在酵母分泌途径中具有重要作用。然而，其作用机制尚不清楚。我们发现，Sec 7结构域家族的所有成员表现出不同的YPT基因的遗传相互作用。生物化学分析表明，尽管Sec 7-结构域家族成员之间的同源性相对较低（20-35%），并且仅限于一个小结构域，但它们都可以作为Arf蛋白的鸟嘌呤核苷酸交换因子（GEF），但不能作为Ypt GTP酶的GEF。Sec 7 p的Sec 7-结构域足以用于该活性。有趣的是，Sec 7结构域活性被布雷菲德菌素A（BFA）抑制，布雷菲德菌素A（BFA）是一种抑制一些Arf-GEF的真菌代谢物，表明该结构域是BFA的靶标。这些结果表明，作为Arf-GEF的能力是酵母中所有Sec 7结构域蛋白的一般性质。在Arf GEFs和Ypt GTP酶之间观察到的遗传相互作用表明在分泌途径中存在Ypt-Arf GTP酶级联。
Two families of GTPases, Arfs and Ypt/rabs, are key regulators of vesicular transport. While Arf proteins are implicated in vesicle budding from the donor compartment, Ypt/rab proteins are involved in the targeting of vesicles to the acceptor compartment. Recently, we have shown a role for Ypt31/32p in exit from the yeast trans-Golgi, suggesting a possible function for Ypt/rab proteins in vesicle budding as well. Here we report the identification of a new member of the Sec7-domain family, SYT1, as a high-copy suppressor of a ypt31/32 mutation. Several proteins that belong to the Sec7-domain family, including the yeast Gea1p, have recently been shown to stimulate nucleotide exchange by Arf GTPases. Nucleotide exchange by Arf GTPases, the switch from the GDP- to the GTP-bound form, is thought to be crucial for their function. Sec7p itself has an important role in the yeast secretory pathway. However, its mechanism of action is not yet understood. We show that all members of the Sec7-domain family exhibit distinct genetic interactions with the YPT genes. Biochemical assays demonstrate that, although the homology between the members of the Sec7-domain family is relatively low (20-35%) and limited to a small domain, they all can act as guanine nucleotide exchange factors (GEFs) for Arf proteins, but not for Ypt GTPases. The Sec7-domain of Sec7p is sufficient for this activity. Interestingly, the Sec7 domain activity is inhibited by brefeldin A (BFA), a fungal metabolite that inhibits some of the Arf-GEFs, indicating that this domain is a target for BFA. These results demonstrate that the ability to act as Arf-GEFs is a general property of all Sec7-domain proteins in yeast. The genetic interactions observed between Arf GEFs and Ypt GTPases suggest the existence of a Ypt-Arf GTPase cascade in the secretory pathway.