Institute of Microbial Chemistry, Tokyo, Tokyo 141-0021, Japan.
Mol Cell. 2011 Nov 4;44(3):462-75. doi: 10.1016/j.molcel.2011.08.035.
E1 enzymes activate ubiquitin-like proteins and transfer them to cognate E2 enzymes. Atg7, a noncanonical E1, activates two ubiquitin-like proteins, Atg8 and Atg12, and plays a crucial role in autophagy. Here, we report crystal structures of full-length Atg7 and its C-terminal domain bound to Atg8 and MgATP, as well as a solution structure of Atg8 bound to the extreme C-terminal domain (ECTD) of Atg7. The unique N-terminal domain (NTD) of Atg7 is responsible for Atg3 (E2) binding, whereas its C-terminal domain is comprised of a homodimeric adenylation domain (AD) and ECTD. The structural and biochemical data demonstrate that Atg8 is initially recognized by the C-terminal tail of ECTD and is then transferred to an AD, where the Atg8 C terminus is attacked by the catalytic cysteine to form a thioester bond. Atg8 is then transferred via a trans mechanism to the Atg3 bound to the NTD of the opposite protomer within a dimer.
E1 酶激活泛素样蛋白并将其转移到同源 E2 酶。Atg7 是一种非典型的 E1，可激活两种泛素样蛋白 Atg8 和 Atg12，并在自噬中发挥关键作用。在这里，我们报告了全长 Atg7 及其与 Atg8 和 MgATP 结合的 C 端结构域的晶体结构，以及与 Atg7 的极端 C 端结构域 (ECTD) 结合的 Atg8 的溶液结构。Atg7 的独特 N 端结构域 (NTD) 负责与 Atg3 (E2) 结合，而其 C 端结构域由同源二聚体腺苷酸化结构域 (AD) 和 ECTD 组成。结构和生化数据表明，Atg8 最初被 ECTD 的 C 端尾巴识别，然后被转移到 AD 上，在 AD 上，Atg8 的 C 端被催化半胱氨酸攻击形成硫酯键。然后，Atg8 通过反式机制转移到与二聚体中相反的前体的 NTD 结合的 Atg3 上。
