Interaction of the human erythrocyte Band 3 anion exchanger 1 (AE1, SLC4A1) with lipids and glycophorin A: Molecular organization of the Wright (Wr) blood group antigen

Abstract

The Band 3 (AE1, SLC4A1) membrane protein is found in red blood cells and in kidney where it functions as an electro-neutral chloride/bicarbonate exchanger. In this study, we have used molecular dynamics simulations to provide the first realistic model of the dimeric membrane domain of human Band 3 in an asymmetric lipid bilayer containing a full complement of phospholipids, including phosphatidylinositol 4,5–bisphosphate (PIP2) and cholesterol, and its partner membrane protein Glycophorin A (GPA). The simulations show that the annular layer in the inner leaflet surrounding Band 3 was enriched in phosphatidylserine and PIP2 molecules. Cholesterol was also enriched around Band 3 but also at the dimer interface. The interaction of these lipids with specific sites on Band 3 may play a role in the folding and function of this anion transport membrane protein. GPA associates with Band 3 to form the Wright (Wr) blood group antigen, an interaction that involves an ionic bond between Glu658 in Band 3 and Arg61 in GPA. We were able to recreate this complex by performing simulations to allow the dimeric transmembrane portion of GPA to interact with Band 3 in a model membrane. Large-scale simulations showed that the GPA dimer can bridge Band 3 dimers resulting in the dynamic formation of long strands of alternating Band 3 and GPA dimers.

Molecular Simulations of Intact Anion Exchanger 1 Reveal Specific Domain and Lipid Interactions

“…The coordinates of the mdAE1 (residues 382–887) were obtained from the crystal structure Protein Data Bank (PDB): 4YZF ( 7 , 37 ). The models were built without the inhibitor DIDS that is present in the crystal structure.…”

“…To model the protein secondary and tertiary structure, an elastic network model with a cut-off distance of 7 Å was used. The elastic network model used in this study is a network that is fairly standard for simulations with the Martini force field, and it was used in a large number of studies that showed good agreement with experimental data, including our previous study on AE1 ( 37 , 44 ). The distance between the dimeric cytoplasmic and membrane domains is greater than the aforementioned 7 Å cut-off distance that was used for the elastic network model (∼24 and ∼20 Å for the rev-V and the V conformers, respectively).…”

Effects of Cholesterol on Membrane Stability of Human Erythrocytes

“…27) In DIDS-modified erythrocytes, the hypotonic hemolysis is enhanced, whereas the hemolysis at 200 MPa is suppressed. 26) Interestingly, in cholesterol-depleted erythrocytes that exhibit a decreased surface area-to-volume ratio, 28,29) hypotonic hemolysis 15) and pressure-induced one are enhanced. Taken together, the hypotonic hemolysis of erythrocytes is enhanced upon reduction of the surface area-to-volume ratio, whereas pressure-induced hemolysis is independent.…”

Plant transporters involved in combating boron toxicity: beyond 3D structures

“…Studies of transporters are often complemented by MD simulations to gain insights into the dynamics of transporters. This dynamic is affected by oligomeric assemblies and how they perturb membrane properties in bilayers forming unique protein–lipid fingerprints [ 66 ]; those may also affect elevator movements [ 67 ].…”