TheSynechocystisManganese Exporter Mnx Is Essential for Manganese Homeostasis in Cyanobacteria.
The essential micronutrient manganese (Mn) functions as redox-active cofactor in active sites of enzymes and, thus, is involved in various physiological reactions. Moreover, in oxygenic photosynthetic organisms, Mn is of special importance, since it is central to the oxygen-evolving complex in photosystem II. Although Mn is an essential micronutrient, increased amounts are detrimental to the organism; thus, only a small window exists for beneficial concentrations. Accordingly, Mn homeostasis must be carefully maintained. In contrast to the well-studied uptake mechanisms in cyanobacteria, it is largely unknown how Mn is distributed to the different compartments inside the cell. We identified a protein with so far unknown function as a hypothetical Mn transporter in the cyanobacterial model strainSynechocystissp. PCC 6803 and named this protein Mnx for Mn exporter. The knockout mutant Δmnxshowed increased sensitivity toward externally supplied Mn and Mn toxicity symptoms, which could be linked to intracellular Mn accumulation.54Mn chase experiments demonstrated that the mutant was not able to release Mn from the internal pool. Microscopic analysis of a Mnx::yellow fluorescent protein fusion showed that the protein resides in the thylakoid membrane. Heterologous expression ofmnxsuppressed the Mn-sensitive phenotype of theSaccharomyces cerevisiaemutant Δpmr1Our results indicate that Mnx functions as a thylakoid Mn transporter and is a key player in maintaining Mn homeostasis inSynechocystissp. PCC 6803. We propose that Mn export from the cytoplasm into the thylakoid lumen is crucial to prevent toxic cytoplasmic Mn accumulation and to ensure Mn provision to photosystem II.
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Fabian
0000-0002-5910-765X
F
Brandenburg
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Hanan
H
Schoffman
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Samantha
0000-0002-6853-1399
S
Kurz
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Ute
0000-0001-7870-4508
U
Krämer
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Nir
N
Keren
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Andreas P M
0000-0003-0970-4672
AP
Weber
Institute of Plant Biochemistry, Cluster of Excellence on Plant Science, Heinrich Heine University, 40225 Duesseldorf, Germany (F.B., S.K., A.P.M.W., M.E.).|Department of Plant and Environmental Sciences, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel (H.S., N.K.); and.|Department of Plant Physiology, Ruhr University, 44801 Bochum, Germany (U.K.).
Marion
0000-0002-2743-8630
M
Eisenhut
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D055785:Gene Knockdown Techniques; D006706:Homeostasis; D017136:Ion Transport; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D008856:Microscopy, Fluorescence; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism
D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria; D008345:Manganese