4KY9

Structural and Functional Analysis of a Putative Substrate Access Tunnel in the Cytosolic Domain of Human Anion Exchanger 1

Summary for 4KY9

• Entry DOI: 10.2210/pdb4ky9/pdb
• Descriptor: Band 3 anion transport protein (2 entities in total)
• Functional Keywords: membrane protein, cytosolic domain
• Biological source: Homo sapiens (human)
• Cellular location: Cell membrane; Multi-pass membrane protein: P02730
• Total number of polymer chains: 2
• Total formula weight: 68429.72

Authors

Shnitsar, V.,Calmettes, C.,Reithmeier, R.A.F.,Moraes, T.F. (deposition date: 2013-05-28, release date: 2013-10-23, Last modification date: 2024-02-28)

Primary citation

Shnitsar, V.,Li, J.,Li, X.,Calmettes, C.,Basu, A.,Casey, J.R.,Moraes, T.F.,Reithmeier, R.A.
A substrate access tunnel in the cytosolic domain is not an essential feature of the solute carrier 4 (SLC4) family of bicarbonate transporters.
J.Biol.Chem., 288:33848-33860, 2013

PubMed Abstract: Anion exchanger 1 (AE1; Band 3; SLC4A1) is the founding member of the solute carrier 4 (SLC4) family of bicarbonate transporters that includes chloride/bicarbonate AEs and Na(+)-bicarbonate co-transporters (NBCs). These membrane proteins consist of an amino-terminal cytosolic domain involved in protein interactions and a carboxyl-terminal membrane domain that carries out the transport function. Mutation of a conserved arginine residue (R298S) in the cytosolic domain of NBCe1 (SLC4A4) is linked to proximal renal tubular acidosis and results in impaired transport function, suggesting that the cytosolic domain plays a role in substrate permeation. Introduction of single and double mutations at the equivalent arginine (Arg(283)) and at an interacting glutamate (Glu(85)) in the cytosolic domain of human AE1 (cdAE1) had no effect on the cell surface expression or the transport activity of AE1 expressed in HEK-293 cells. In addition, the membrane domain of AE1 (mdAE1) efficiently mediated anion transport. A 2.1-Å resolution crystal structure of cdΔ54AE1 (residues 55-356 of cdAE1) lacking the amino-terminal and carboxyl-terminal disordered regions, produced at physiological pH, revealed an extensive hydrogen-bonded network involving Arg(283) and Glu(85). Mutations at these residues affected the pH-dependent conformational changes and stability of cdΔ54AE1. As these structural alterations did not impair functional expression of AE1, the cytosolic and membrane domains operate independently. A substrate access tunnel within the cytosolic domain is not present in AE1 and therefore is not an essential feature of the SLC4 family of bicarbonate transporters.

PubMed: 24121512
DOI: 10.1074/jbc.M113.511865

Experimental method

X-RAY DIFFRACTION (2.23 Å)