Figure 3. Construct designs and data summary from experiments that explore regions upstream of the cationic cluster.

A, designs of constructs. In addition to Δ9_40–48 (see Fig. 1A), we created 5 additional deletion constructs, based on NBCe1‐B (B_WT). B, HCO₃ ⁻‐dependent conductances (G _HCO3) computed between −20 and +20 mV of I−V relationships. G _HCO3 values were normalized to the G _HCO3 from an oocyte – studied the same day – expressing ∆9_40–48. The n for each group (i.e. construct) is 6. Asterisks indicate significant differences, by one‐way ANOVA followed by post hoc Tukey's comparison. C, surface‐biotinylated proteins, analysed by western blotting. The 7 contiguous lanes (the H₂O is virtually blank) of the blot are aligned with the labels in B. This blot is representative of two trials, which confirm that ∆12_28–39 is present at relatively low abundance in the plasma membrane. D, HCO₃ ⁻‐dependent conductances (G _HCO3) from oocytes expressing seven different constructs, without or with super‐IRBIT (sIRBIT). G _HCO3 values were normalized to the G _HCO3 from an oocyte – studied the same day – expressing ∆9_40–48 without sIRBIT. The n for each group is 3–6. ^†Pairs are significantly different in a one‐tailed, unpaired t test. NS, not significant. ^#Grey bar is significantly different from the other grey bars in an ANOVA with Tukey's post hoc comparison.