Shiba Tomoo, Kawasaki Masato, Takatsu Hiroyuki, Nogi Terukazu, Matsugaki Naohiro, Igarashi Noriyuki, Suzuki Mamoru, Kato Ryuichi, Nakayama Kazuhisa, Wakatsuki Soichi
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
Nat Struct Biol. 2003 May;10(5):386-93. doi: 10.1038/nsb920.
GGAs are critical for trafficking soluble proteins from the trans-Golgi network (TGN) to endosomes/lysosomes through interactions with TGN-sorting receptors, ADP-ribosylation factor (ARF) and clathrin. ARF-GTP bound to TGN membranes recruits its effector GGA by binding to the GAT domain, thus facilitating recognition of GGA for cargo-loaded receptors. Here we report the X-ray crystal structures of the human GGA1-GAT domain and the complex between ARF1-GTP and the N-terminal region of the GAT domain. When unbound, the GAT domain forms an elongated bundle of three a-helices with a hydrophobic core. Structurally, this domain, combined with the preceding VHS domain, resembles CALM, an AP180 homolog involved in endocytosis. In the complex with ARF1-GTP, a helix-loop-helix of the N-terminal part of GGA1-GAT interacts with the switches 1 and 2 of ARF1 predominantly in a hydrophobic manner. These data reveal a molecular mechanism underlying membrane recruitment of adaptor proteins by ARF-GTP.
GGA蛋白对于通过与反式高尔基体网络（TGN）分选受体、ADP核糖基化因子（ARF）和网格蛋白相互作用，将可溶性蛋白从反式高尔基体网络转运至内体/溶酶体至关重要。结合在TGN膜上的ARF-GTP通过与GAT结构域结合招募其效应器GGA，从而促进GGA对装载货物的受体的识别。在此，我们报道了人GGA1-GAT结构域以及ARF1-GTP与GAT结构域N端区域复合物的X射线晶体结构。未结合时，GAT结构域形成一个由三个α螺旋组成的细长束，带有一个疏水核心。在结构上，该结构域与前面的VHS结构域相结合，类似于参与内吞作用的AP180同源物CALM。在与ARF1-GTP形成的复合物中，GGA1-GAT N端部分的一个螺旋-环-螺旋主要以疏水方式与ARF1的开关1和开关2相互作用。这些数据揭示了ARF-GTP介导衔接蛋白膜招募的分子机制。
