Abstract

Aquaporins (AQPs) belong to a transmembrane protein superfamily composed of an internal repeat of a three membrane-spanning domain and each has a highly conserved NPA box. Based on the more variable carboxyl-terminal NPA box, AQPs can be divided into three subfamilies: (1) glycerol-channel aquaglyceroporin (gAQP) (2) water-selective AQP (wAQP), and (3) deviated superaquaporin (sAQP) in the order of passible evolution. This classification has functional and localization relevance: most wAQPs transports water selectively whereas gAQPs and sAQPs also transport small molecules with sAQPs mostly localized inside the cell. As this classification is not based on the function, some wAQPs functioning as glycerol channels will not be included in gAQPs. AQP ancestors may have first originated in eubacteria as gAQPs to transport small molecules such as glycerol. Later some of them may have acquired a water-selective filter to become wAQPs. Although AQPs are absent in many bacteria, especially in archaea, both gAQPs and wAQPs may have been carried over to eukaryotes or horizontally transferred. Finally, multicellular organisms have obtained new sAQPs, which are curiously absent in fungi and plants. Interestingly, both plants and higher insects independently have lost gAQPs, whose functions, however, have been taken over by functionally modified wAQPs partly obtained by horizontal gene transfers from bacteria. This evolutionary viewpoints on AQPs will facilitate further functional analysis of AQP-like sequences and expand our viewpoints on AQP superfamily.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.