Structural basis for the Rho- and phosphoinositide-dependent localization of the exocyst subunit Sec3
Structural basis for the Rho- and phosphoinositide-dependent localization of the exocyst subunit Sec3
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DOI：
10.1038/nsmb.1722
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发表时间：
2010-02-01
影响因子：
16.8
通讯作者：
Fukai, Shuya
中科院分区：
文献类型：
--
作者：
Yamashita, Masami;Kurokawa, Kazuo;Fukai, Shuya
外囊复合体是一种异八聚体蛋白质复合体，在细胞极化过程中通过将分泌囊泡连接到靶膜来发挥作用。酵母外囊亚单位Sec3通过其N-末端结构域(Sec3-N)与磷脂酰肌醇4，5-二磷酸(PtdIns(4，5)P-2)以及小的GTP酶Rho1和CDc42结合，这些相互作用将Sec3靶向质膜。本文报道了在2.6埃分辨率下，Sec3-N与Rho1形成的络合物的晶体结构。Sec3-N采用Pleckstrin同源(PH)折叠，尽管与已知结构的其他PH结构域没有可检测到的序列同源性。一簇保守的碱性残基构成一个带正电的裂隙，它被确定为PtdIns(4，5)P2的结合位点。Sec3的Phe77、Ile115和Leu131残基与Rho1的切换区I和II周围形成的延伸的疏水表面结合。据我们所知，这是第一次对外囊亚基如何与靶膜上的蛋白质和磷脂因子相互作用的结构性见解。
The exocyst complex is a hetero-octameric protein complex that functions during cell polarization by tethering the secretory vesicle to the target membrane. The yeast exocyst subunit Sec3 binds to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P-2) and the small GTPases Rho1 and Cdc42 via its N-terminal domain (Sec3-N), and these interactions target Sec3 to the plasma membrane. Here we report the crystal structure of the Sec3-N in complex with Rho1 at 2.6-angstrom resolution. Sec3-N adopts a pleckstrin homology (PH) fold, despite having no detectable sequence homology with other PH domains of known structure. Clusters of conserved basic residues constitute a positively charged cleft, which was identified as a binding site for PtdIns(4,5) P2. Residues Phe77, Ile115 and Leu131 of Sec3 bind to an extended hydrophobic surface formed around switch regions I and II of Rho1. To our knowledge, these are the first structural insights into how an exocyst subunit might interact with both protein and phospholipid factors on the target membrane.