Aquaporin-11 (AQP-11) is an endoplasmic reticulum-localized water channel essential for renal development. Its structure and the molecular basis of its transport properties remained unknown. We analyzed the human AQP11 structure under cryo–electron microscopy at 2.3 Å resolution, revealing a trimeric architecture compared with other known tetrameric AQPs and a topology comprising seven transmembrane helices (Hs), including an additional N-terminal helix (H0). The channel pore is broader and more hydrophobic than that of canonical AQPs, and features a unique structure surrounding an Asn-Pro-Cys (NPC) sequence instead of the typical Asn-Pro-Ala (NPA) motif. These features provide a structural framework through which water and other small solutes can permeate AQP11. Our findings provide a blueprint for designing specific inhibitors to investigate the physiologic functions of AQP11.
Suzuki et al. (Fri,) studied this question.