Related Experiment Video
Updated: Aug 14, 2025

Sample Preparation using a Lipid Monolayer Method for Electron Crystallographic Studies
Published on: November 20, 2021
The structural basis for glycerol permeation by human AQP7
Li Zhang1, Deqiang Yao2, Ying Xia3
1CAS Center for Excellence on Molecular Cell Science, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 201210, China.
Abstract:
Human glycerol channel aquaporin 7 (AQP7) conducts glycerol release from adipocyte and enters the cells in pancreatic islets, muscles, and kidney tubules, and thus regulates glycerol metabolism in those tissues. Compared with other human aquaglyceroporins, AQP7 shows a less conserved "NPA" motif in the center cavity and a pair of aromatic residues at Ar/R selectivity filter. To understand the structural basis for the glycerol conductance, we crystallized the human AQP7 and determined the structure at 3.7 Å. A substrate binding pocket was found near the Ar/R filter where a glycerol molecule is bound and stabilized by R229. Glycerol uptake assay on human AQP7 as well as AQP3 and AQP10 demonstrated strong glycerol transportation activities at the physiological condition. The human AQP7 structure, in combination with the molecular dynamics simulation thereon, reveals a fully closed conformation with its permeation pathway strictly confined by the Ar/R filter at the exoplasmic side and the gate at the cytoplasmic side, and the binding of glycerol at the Ar/R filter plays a critical role in controlling the glycerol flux by driving the dislocation of the residues at narrowest parts of glycerol pathway in AQP7.
Related Concept Videos
Aquaporins
Carrier-Mediated Transport
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
The Significance of Membrane Transport
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
Drug Absorption Mechanism: Passive Membrane Transport
Pore Transport and Ion-Pair Transport
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct...
Mechanisms of Drug Absorption: Paracellular, Transcellular, and Vesicular Transport
However, most drugs use the transcellular route, traversing directly through the cell membranes via two mechanisms: passive and active transport. Passive...

