Molecular mechanism of ubiquitin recognition by GGA3 GAT domain
Molecular mechanism of ubiquitin recognition by GGA3 GAT domain
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DOI：
10.1111/j.1365-2443.2005.00865.x
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发表时间：
2005-07-01
期刊：
影响因子：
2.1
通讯作者：
Wakatsuki, S
中科院分区：
文献类型：
--
作者：
Kawasaki, M;Shiba, T;Wakatsuki, S
GGA（Golgi-localizing，gamma-adaptin ear domain homology，ARF-binding）蛋白是网格蛋白外壳接头蛋白家族的一员，通过GAT（GGA and Tom 1）结构域的C端三螺旋束（C-GAT）与泛素的相互作用参与泛素依赖的受体分选。我们在这里报告的晶体结构的人GGA 3 C-GAT的复合物与泛素。C-GAT螺旋α 1和α 2上的疏水补丁形成泛素疏水Ile 44表面的结合位点。泛素Arg 42的两种不同取向决定了泛素Ile 44表面的形状和电荷分布，导致两种不同的结合模式。生物化学和NMR数据强烈表明，C-GAT螺旋α 2和α 3上的另一个疏水结合位点，与第一个结合位点相反，也结合泛素，尽管很弱。泛素的双面结合为GAT结构域提供了更高的识别泛素化受体的效率，用于溶酶体受体降解。
GGA (Golgi-localizing, gamma-adaptin ear domain homology, ARF-binding) proteins, which constitute a family of clathrin coat adaptor proteins, have recently been shown to be involved in the ubiquitin-dependent sorting of receptors, through the interaction between the C-terminal three-helix-bundle of the GAT (GGA and Tom1) domain (C-GAT) and ubiquitin. We report here the crystal structure of human GGA3 C-GAT in complex with ubiquitin. A hydrophobic patch on C-GAT helices alpha 1 and alpha 2 forms a binding site for the hydrophobic Ile44 surface of ubiquitin. Two distinct orientations of ubiquitin Arg42 determine the shape and the charge distribution of ubiquitin Ile44 surface, leading to two different binding modes. Biochemical and NMR data strongly suggest another hydrophobic binding site on C-GAT helices alpha 2 and alpha 3, opposite to the first binding site, also binds ubiquitin although weakly. The double-sided ubiquitin binding provides the GAT domain with higher efficiency in recognizing ubiquitinated receptors for lysosomal receptor degradation.