AQUAPORINS AS A WATER CHANNEL PROTEINS

Shahid Raza and Hira Mubeen*

ABSTRACT

Aquaporins are water channel membrane proteins found as a part of major intrinsic protein (MIP) superfamily. MIP was considered as the basis for nomenclature PIP, TIP and NIP also indicating the subcellular localization plasma membrane, tonoplast and nodule of the respective founding member. More than 150 MIPs have been identified in organisms ranging from bacteria to animals and plants. In plants, aquaporins are present in the plasma membrane and in the vacuolar membrane where they are abundant constituents. Plants contain a large number of aquaporin isoforms with distinct cell type- and tissue-specific expression patterns. Some of these are constitutively expressed, whereas the expression of others is regulated in response to environmental factors, such as drought and salinity. Studies suggested the role for aquaporins in regulating transmembrane water transport during the growth, development, and stress responses of plants. Hence it is suggested to research out the integrated functions of aquaporin in water transport and to explore its more functions as a transport protein.

Keywords: Transmembrane, MIP, constitutively, salinity.