Identification and characterization of the Na+/H+ antiporter Nhas3 from the thylakoid membrane of Synechocystis sp. PCC 6803.
Na+/H+ antiporters influence proton or sodium motive force across the membrane. Synechocystis sp. PCC 6803 has six genes encoding Na+/H+ antiporters, nhaS1-5 and sll0556. In this study, the function of NhaS3 was examined. NhaS3 was essential for growth of Synechocystis, and loss of nhaS3 was not complemented by expression of the Escherichia coli Na+/H+ antiporter NhaA. Membrane fractionation followed by immunoblotting as well as immunogold labeling revealed that NhaS3 was localized in the thylakoid membrane of Synechocystis. NhaS3 was shown to be functional over a pH range from pH 6.5 to 9.0 when expressed in E. coli. A reduction in the copy number of nhaS3 in the Synechocystis genome rendered the cells more sensitive to high Na+ concentrations. NhaS3 had no K+/H+ exchange activity itself but enhanced K+ uptake from the medium when expressed in an E. coli potassium uptake mutant. Expression of nhaS3 increased after shifting from low CO2 to high CO2 conditions. Expression of nhaS3 was also found to be controlled by the circadian rhythm. Gene expression peaked at the beginning of subjective night. This coincided with the time of the lowest rate of CO2 consumption caused by the ceasing of O2-evolving photosynthesis. This is the first report of a Na+/H+ antiporter localized in thylakoid membrane. Our results suggested a role of NhaS3 in the maintenance of ion homeostasis of H+, Na+, and K+ in supporting the conversion of photosynthetic products and in the supply of energy in the dark.
Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601.
Kenta
K
Tsunekawa
From the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579.
Toshiaki
T
Shijuku
From the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579.
Mitsuo
M
Hayashimoto
Department of Environment and Forest Resources Science, Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529.
Yoichi
Y
Kojima
Center for Gene Research, Nagoya University, Nagoya 464-8602.
Kiyoshi
K
Onai
Center for Gene Research, Nagoya University, Nagoya 464-8602.
Megumi
M
Morishita
Center for Gene Research, Nagoya University, Nagoya 464-8602.
Masahiro
M
Ishiura
Department of Genome Applied Microbiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530.
Teruo
T
Kuroda
Department of Microbiology, Niigata University of Pharmacy and Applied Life Sciences, Niigata 950-2081.
Tatsunosuke
T
Nakamura
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chiba 260-8675.
Hiroshi
H
Kobayashi
RIKEN Plant Science Center, 1-7-22 Suehirocho, Yokohama 230-0045.
Mayuko
M
Sato
RIKEN Plant Science Center, 1-7-22 Suehirocho, Yokohama 230-0045.
Kiminori
K
Toyooka
Laboratory of Plant Nutrition, Faculty of Agriculture, Kyushu University, 6-10-1, Hakozaki, Fukuoka 812-8581, Japan.
Ken
K
Matsuoka
Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601.
Tatsuo
T
Omata
From the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579. Electronic address: uozumi@biophy.che.tohoku.ac.jp.
Nobuyuki
N
Uozumi
D002940:Circadian Rhythm / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics; D006706:Homeostasis / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D010101:Oxygen Consumption / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D011522:Protons; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism*; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics; D020524:Thylakoids / Q000201:enzymology* / Q000235:genetics
D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D011188:Potassium