Zhdankina O, Strand N L, Redmond J M, Boman A L
Department of Biochemistry and Molecular Biology, University of Minnesota, School of Medicine, Duluth, MN 55812, USA.
Yeast. 2001 Jan 15;18(1):1-18. doi: 10.1002/1097-0061(200101)18:1<1::AID-YEA644>3.0.CO;2-5.
ARF proteins regulate the formation of transport vesicles at many steps of the secretory and endocytic pathways. A recently identified family of ARF effectors, named GGAs, appears to regulate membrane traffic exiting the trans-Golgi network in mammalian cells (Boman et al., 2000). We have identified two GGA homologues in the yeast S. cerevisiae. These previously uncharacterized open reading frames, YDR358w and YHR108w, have been named GGA1 and GGA2, respectively. Using the two-hybrid assay and GST-affinity chromatography, we show that Gga1p and Gga2p interact with Arf1p and Arf2p in a GTP-dependent manner, suggesting that both are functional homologues of the human GGA proteins. The Arf-binding domain resides in the amino-terminal half of Gga1p (amino acids 170-330), and the carboxy-terminal 100 amino acids resemble the gamma-adaptin 'ear domain'. Gene deletion experiments indicate that GGA1 and GGA2 are not essential genes, as single and double knockouts are viable at both 30 degrees C and 37 degrees C. However, cells lacking GGA1 and GGA2 exhibit defects in invertase processing and CPY sorting, but not endocytosis. We conclude that yeast Gga proteins are effectors of Arf in yeast that facilitate traffic through the late Golgi.
ARF蛋白在分泌途径和内吞途径的多个步骤中调节转运囊泡的形成。最近鉴定出的一个名为GGAs的ARF效应蛋白家族，似乎在哺乳动物细胞中调节从反式高尔基体网络输出的膜运输（博曼等人，2000年）。我们在酿酒酵母中鉴定出了两个GGA同源物。这两个以前未被表征的开放阅读框，YDR358w和YHR108w，分别被命名为GGA1和GGA2。通过双杂交试验和GST亲和层析，我们发现Gga1p和Gga2p以GTP依赖的方式与Arf1p和Arf2p相互作用，这表明它们都是人类GGA蛋白的功能同源物。Arf结合结构域位于Gga1p的氨基末端一半（第170 - 330个氨基酸），羧基末端的100个氨基酸类似于γ衔接蛋白的“耳结构域”。基因缺失实验表明，GGA1和GGA2不是必需基因，因为单敲除和双敲除在30℃和37℃时都是可行的。然而，缺乏GGA1和GGA2的细胞在转化酶加工和羧肽酶Y分选方面表现出缺陷，但在内吞作用方面没有缺陷。我们得出结论，酵母Gga蛋白是酵母中Arf的效应蛋白，有助于晚期高尔基体的运输。
