Figure 1. Schematic diagram of mouse AQP5 transmembrane topology. NPA (blue circles) represents the highly conserved aquaporin signature sequence. H1–H6, membrane-spanning helices; A–E, loops; loops B and E form pore helices. NH₂- and COOH- amino and carboxyl terminal domains, respectively. Two consensus phosphorylation motifs are present, one at amino acid residues RRTSP at 153–157 in loop D and another, RKKT at 256–259 at the COOH-terminal domain.