STRUCTURAL STUDIES OF ANABAS TESTUDINEUS (CLIMBING PERCH FISH) AQUAPORIN 1AA (AQP1AA) AND OREOCHROMIS MOSSAMBICUS (TILAPIA FISH) CHLORIDE INTRACELLULAR CHANNEL 2 (CLIC2)

Abstract

Water and ion homeostasis are fundamental for all organisms. Living in water, fishes have evolved with effective iono-osmoregulation mechanisms, involving many water and ion channels. Aquaporins are membrane proteins and transport water across membrane. They ubiquitously exist in almost all organisms and play essential biological roles. As fishes are subject to continuous osmotic pressure, we propose fish aquaporins might have unique structural features and be regulated differently, compared to those of terrestrial vertebrates. We successfully determined the crystal structure of aquaporin 1aa from Anabas testudineus (climbing perch, at 1.9 Å resolution) and analyzed the unique structural features to understand its regulation mechanisms. We also determined the crystal structure of chloride intracellular channel 2, a member of the Clics family, from Oreochromis mossambicus (tilapia, at 3 Å resolution). By comparing the structure of tilapia Clic2 with other homologous structures, we could infer their conserved physiological roles.