Figure 6.Biophysical modification of NBC-model Left. Model voltage clamp experiment illustrating the predicted change in the NBC I-V plot after modification by “factor X” in the proximal tubule or eye. Changing from a 1:2 (solid line with squares) to 1:3 (dotted line with circles) Na+:HCO3 - coupling will not only shift ERev, but would likely increase the current measured at the voltage extremes. The basal current at –60mV for 1:3 is also predicted to be much less than we typically measure for NBC, i.e., +200 nA to slight inward current (-50 to -100 nA). Right. Diagram indicating “how” mechanistically a NBCinteracting protein could change ionic coupling. We envision a conformational change in NBC which exposes/opens an additional HCO3 - binding pocket.