Ionic selectivity of NCKX2, NCKX3, and NCKX4 for monovalent cations at K+-binding site.
To determine the ionic selectivity of K+-sites in three members of Na+/Ca2++K+ exchanger (NCKX) family: NCKX2, NCKX3 and NCKX4, we compared the amplitudes of reverse mode NCKX current (I(NCKX)) activated by K+-substitutes (Rb+, NH4+, Cs+, or Li+) relative to that by K+ in an HEK293 cell overexpressing each of NCKX isoforms. In all three isoforms, monovalent cations activated I(NCKX) with similar order of potency: K+ > Rb+ > NH4+ > Cs+ >> Li+. However, the relative potency of Cs+ and NH4+ for activating NCKX2 was significantly higher than those for NCKX3 and NCKX4, indicating that the selectivity of NCKX2 for K+ is weaker than the other two isoforms.
Lee
Ju-Young
JY
Department of Physiology and National Research Laboratory for Cell Physiology, Seoul National University College of Medicine, Yongon-Dong 28, Seoul, 110-799, Korea.
Ho
Won-Kyung
WK
Lee
Suk-Ho
SH
D001665:Binding Sites; D002414:Cations, Monovalent; D006801:Humans; D020033:Protein Isoforms / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
D002414:Cations, Monovalent; D020033:Protein Isoforms; D019831:Sodium-Calcium Exchanger