Structures and receptor binding activities of merbecovirus spike proteins reveal key signatures for human DPP4 adaptation
- Hang Yuan
- Jingjing Wang
- Yong Ma
- Zimu Li
- Xijie Gao
- Gul Habib
- Banghui Liu
- Jing Chen
- Jun He
- Peng Zhou
- Zheng-Li Shi
- Xinwen Chen
- Xiaoli Xiong
2025-07-11
Merbecoviruses from bats, pangolins, and hedgehogs pose significant zoonotic threats, with a limited understanding of receptor binding by their spike (S) proteins. Here, we report cryo-EM structures of GD-BatCoV (BtCoV-422) and SE-PangolinCoV (MjHKU4r-CoV-1) RBDs in complex with human DPP4 (hDPP4). These structures exhibit a substantial offset in their hDPP4 interaction interfaces, revealing a conserved hydrophobic cluster as a convergent signature of DPP4 binding within the MERS-HKU4 clade of merbecoviruses. Structure-guided mutagenesis demonstrates that favorable interactions are distributed across multiple receptor binding motif (RBM) regions, working synergistically to confer high-affinity hDPP4 binding. Swapping of the merbecovirus RBM regions indicate limited plasticity and interchangeability among these regions. In addition, we report cryo-EM structures of six merbecovirus S-trimers. Structure-based phylogenetics suggests that hDPP4-binding merbecoviruses undergo convergent evolution, while ACE2-binding merbecoviruses exhibit diversification in their binding mechanisms. These findings offer critical insights into merbecovirus receptor utilization, providing a structural understanding for future surveillance.