Extended Data Fig. 9: SSM-based electrophysiology measurements of NHA2 ΔN and variants in proteoliposomes.
From: Structure, mechanism and lipid-mediated remodeling of the mammalian Na+/H+ exchanger NHA2
a. Fit of the normalized amplitude of the transient currents as a function of Na+ (Li+) concentrations and pH for bison NHA2ΔN and bison NHA2ΔTM–1 and the corresponding binding affinity (KD). Note, since we are measuring pre-steady-state ion translocation rather than steady-state currents, it is more accurate to refer this estimate as a binding constant (KD) rather than the Michaelis–Menten constant, KM. Currents have been normalized for bison NHA2ΔN 150 mM Na+ at pH 7.5 as indicated by the green square. Error bars are the mean values ± s.d. of: n = 6 independent experiments (sensors) for bison NHA2ΔN with NaCl; n = 7 independent experiments (sensors) for bison NHA2ΔTM-1 with NaCl; n = 3 independent experiments (sensors) for bison NHA2ΔN and bison NHA2ΔN with LiCl b. The fit of the normalized amplitudes for bison NHA2ΔN and derived variants W456F and E214R-R431E recorded after Li+ concentration jumps at symmetrical pH 7.5 (left) and for the variant T461E (right). Error bars are the mean values ± s.d. of n = 3 independent experiments (sensors) c. As in b. for NaCl additions. Error bars are the mean values ± s.d. of n = 3 independent experiments (sensors). Note, the either the weak or no binding observed for the T461E variant with Li+ and Na+ addition respectively, is consistent with the lack of complementation to Li+ or Na+ salt-stress in the AB11c strain (Supplementary Fig. 3d-e).
