Figure 3.

Quantitation of XENaC^F surface expression with iodinated anti-FLAG antibody. (A) XENaC^F and XENaC^F + XK-Ras2A^G12V–expressing oocytes showed a similarly high I_ami, in contrast to the small current of the XENaC^F–expressing ones treated with progesterone. (B) From the heterotetramer building the channel (2α, 1β, 1γ) (Firsov et al., 1998), three subunits out of four (2α and 1β) were tagged with a FLAG epitope. The antibody binding to surface XENaC^F was quantitated as described by Firsov et al. (1996)for the rat ENaC^F. Maturating oocytes showed a significantly lower number of binding sites such that I_ami per surface-expressed XENaC^F (C) was higher in XK-Ras2A^G12V–coinjected oocytes than in those expressing XENaC^F alone in the presence or absence of progesterone. Results are expressed as means of five independent experiments ± SEM with each of four to nine oocytes per group.