Premium
The Dual Roles of Aromatic Residue Y67 in Claudin‐2 Pore Cation Selectivity
Author(s) -
Li Jiahua,
Zhuo Min,
Pei Lei,
Yu Alan S.L.
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.954.1
Subject(s) - selectivity , chemistry , paracellular transport , claudin , steric effects , extracellular , residue (chemistry) , side chain , divalent , biophysics , amino acid , permeability (electromagnetism) , stereochemistry , biochemistry , tight junction , organic chemistry , membrane , catalysis , polymer , biology
In tight junctions, claudin‐2 forms a paracellular cation selective pore by interaction of the first extracellular loop (ECL 1). When all negatively charged residues in the claudin‐2 ECL 1 were mutated to neutral amino acids, the pore became less cation selective but remained four times more selective to Na+ than to Cl‐, suggesting other non‐charged amino acids may also contribute to cation selectivity. We hypothesized that Y67, a conserved aromatic residue near the pore selective filter, contributed to cation selectivity by cation‐pi interaction with the permeating cation. We generated stably transfected claudin‐2 Y67 mutants in MDCK I Tet‐off cells. Y67L partially lost cation selectivity due to decreased Na+ permeability without affecting Cl‐ permeability. Y67A enlarged the pore size and further decreased cation selectivity due to an increase in Cl‐ permeability. The Y67C accessibility assay suggested Y67's side chain pointing to the lumen of the pore. In conclusion, we demonstrate that the conserved aromatic residue at site 67 contributes to cation selectivity by a dual role of a cation‐pi interaction and a steric effect. Supported by NIH grants R01DK062283, R01DK062283–07S1 and U01GM094627.