Kong Chunguang, Ito Koichi, Walsh Martin A, Wada Miki, Liu Yuying, Kumar Sundramurthy, Barford David, Nakamura Yoshikazu, Song Haiwei
Laboratory of Macromolecular Structure, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Japan.
Mol Cell. 2004 Apr 23;14(2):233-45. doi: 10.1016/s1097-2765(04)00206-0.
Translation termination in eukaryotes is governed by two interacting release factors, eRF1 and eRF3. The crystal structure of the eEF1alpha-like region of eRF3 from S. pombe determined in three states (free protein, GDP-, and GTP-bound forms) reveals an overall structure that is similar to EF-Tu, although with quite different domain arrangements. In contrast to EF-Tu, GDP/GTP binding to eRF3c does not induce dramatic conformational changes, and Mg(2+) is not required for GDP binding to eRF3c. Mg(2+) at higher concentration accelerates GDP release, suggesting a novel mechanism for nucleotide exchange on eRF3 from that of other GTPases. Mapping sequence conservation onto the molecular surface, combined with mutagenesis analysis, identified the eRF1 binding region, and revealed an essential function for the C terminus of eRF3. The N-terminal extension, rich in acidic amino acids, blocks the proposed eRF1 binding site, potentially regulating eRF1 binding to eRF3 in a competitive manner.
真核生物中的翻译终止由两个相互作用的释放因子eRF1和eRF3控制。粟酒裂殖酵母eRF3的eEF1α样区域在三种状态（游离蛋白、GDP结合形式和GTP结合形式）下测定的晶体结构显示，其整体结构与EF-Tu相似，尽管结构域排列有很大不同。与EF-Tu不同，GDP/GTP与eRF3c的结合不会引起显著的构象变化，并且GDP与eRF3c的结合不需要Mg(2+)。较高浓度的Mg(2+)会加速GDP的释放，这表明eRF3上核苷酸交换的机制与其他GTP酶不同。将序列保守性映射到分子表面，并结合诱变分析，确定了eRF1结合区域，并揭示了eRF3 C末端的重要功能。富含酸性氨基酸的N末端延伸阻断了提议的eRF1结合位点，可能以竞争性方式调节eRF1与eRF3的结合。
