IRBIT neither activates nor binds to AE2 (A) Sequence alignment between (1–79) N-terminal domain of NBCe1-B as a putative IRBIT binding module and N- terminal cytoplasmic domain of AE2. (B and C) HeLa cells were transfected with GFP, IRBIT, AE2, or AE2 + IRBIT. CBE activity was assessed by the slope of pHi in the absence of Cl− at the beginning of time course (30 ∼45 sec) and height to reach the maximum pHi point from the minimum point. The bars show the mean ± SEM. (D) The Co-IP of IRBIT with AE2. NBCe1-B was tagged with GFP and IRBIT was tagged with flag. Anti-GFP, anti-HA, and anti-flag antibodies were used for the Co-IP. Input actin was used as a loading control. The (-) represented cell lysates.