title: Functional characterization and hyperosmotic regulation of aquaporin in Synechocystis sp. PCC 6803.
abstract: The genome of the cyanobacterium Synechocystis sp. PCC 6803 (hereafter, Synechocystis) contains an aqpZ gene (slr2057) which encodes an aquaporin (SsAqpZ), a membrane channel protein that might play a role in osmotic water transport and therefore the growth of Synechocystis. Structural characterization of SsAqpZ by protein sequence analysis and homology modelling revealed that it was more similar to bacterial aquaporin Z than the glycerol facilitator. To understand the functional role of SsAqpZ, the aqpZ knockout (KO) and myc-tagged aqpZ knockin (KI) Synechocystis were constructed. Water channel activity assays showed that SsAqpZ facilitated water transportation. SsAqpZ-mediated changes in cell volume were observed in wild-type (WT) and KI Synechocystis. Expression of SsAqpZ in KI Synechocystis was induced by extracellular hyperosmolarity. In the absence of hyperosmolarity, WT, KO and KI Synechocystis showed the same pattern of growth and no morphological or phenotypical perturbations. Under hyperosmotic condition, while the WT and also KI cells maintained a similar growth rate throughout the entire exponential phase, KO cells grew significantly slower. These results indicate that SsAqpZ has water channel activity and is involved in the adaptation and maintenance of growth of Synechocystis in a hyperosmotic environment.
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan. dakazad-btc@sust.edu
authors.forename: Abul Kalam
authors.initials: AK
authors.lastname: Azad
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sato
authors.forename: Kai
authors.initials: K
authors.lastname: Ohtani
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibata
mesh_terms: D000595:Amino Acid Sequence; D020346:Aquaporins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D055879:Gene Knock-In Techniques; D055786:Gene Knockout Techniques; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009997:Osmotic Pressure; D010802:Phylogeny; D046939:Synechocystis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D014867:Water