Figure 6
Functional properties and subcellular localization of wild-type (WT) sea bream Aqp1a and Aqp1b, and of their chimeric proteins, in oocytes. (A) Membrane topology of AQP family members showing the six transmembrane helices with five connecting loops (A-E), and two conserved Asn-Pro-Ala (NPA) motifs in loops B and E. (B-E) WT Aqp1a (B) and Aqp1b (C), Aqp1a chimera in which the C-terminus of Aqp1a was exchanged with that of Aqp1b (Aqp1a-Ct1b; D), and Aqp1b chimera in which the C-terminus of Aqp1b was exchanged with that of Aqp1a (Aqp1b-Ct1a; E). (F) Pf of oocytes expressing 1 ng of cRNA encoding WT or chimeric proteins. Values represent the mean ± SEM (n = 5–8 oocytes) from a representative experiment. The asterisk denotes statistically significant differences (p < 0.01). (G-J) Immunofluorescence microscopy of oocytes localizing WT Aqp1a and Aqp1b-Ct1a exclusively at the plasma membrane, whereas WT Aqp1b and Aqp1a-Ct1b are also in the cytoplasm. Sections shown in G and J were probed with the anti-Aqp1a antisera, whereas the sections in H and I were probed with the anti-Aqp1b antisera. Bar, 50 μm. (K-L) Immunoblots of total and plasma membrane equivalents (TM and PM, respectively) of oocytes expressing the differents cRNAs. Blots were probed as indicate above. The apparent molecular mass of a 29-kDa marker is indicated on the left.