In vitro analyses of mitochondrial ATP/phosphate carriers from Arabidopsis thaliana revealed unexpected Ca2+-effects

BMC Plant Biology

Research Article

Ilka Haferkamp¹  André Lorenz¹  Melanie Lorenz¹  Ute C. Vothknecht²  H. Ekkehard Neuhaus³  Sandra Niopek-Witz³ 

[1] Cellular Physiology/Membrane Transport, University of Kaiserslautern, 67653, Kaiserslautern, Germany;Department of Biology I, Botany, LMU Munich, Großhaderner Str. 2, D-82152, Planegg-Martinsried, Germany;Plant Physiology, University of Kaiserslautern, 67653, Kaiserslautern, Germany;

关键词: Mitochondria;    calcium;    Ca;    Signaling;    Energy;    Adenine nucleotide transport;    Plant;    ATP;    ADP;    Phosphate;   

DOI  :  10.1186/s12870-015-0616-0

 received in 2015-06-25, accepted in 2015-09-12,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundAdenine nucleotide/phosphate carriers (APCs) from mammals and yeast are commonly known to adapt the mitochondrial adenine nucleotide pool in accordance to cellular demands. They catalyze adenine nucleotide - particularly ATP-Mg - and phosphate exchange and their activity is regulated by calcium. Our current knowledge about corresponding proteins from plants is comparably limited. Recently, the three putative APCs from Arabidopsis thaliana were shown to restore the specific growth phenotype of APC yeast loss-of-function mutants and to interact with calcium via their N-terminal EF-hand motifs in vitro. In this study, we performed biochemical characterization of all three APC isoforms from A. thaliana to gain further insights into their functional properties.ResultsRecombinant plant APCs were functionally reconstituted into liposomes and their biochemical characteristics were determined by transport measurements using radiolabeled substrates. All three plant APCs were capable of ATP, ADP and phosphate exchange, however, high preference for ATP-Mg, as shown for orthologous carriers, was not detectable. By contrast, the obtained data suggest that in the liposomal system the plant APCs rather favor ATP-Ca as substrate. Moreover, investigation of a representative mutant APC protein revealed that the observed calcium effects on ATP transport did not primarily/essentially involve Ca2+-binding to the EF-hand motifs in the N-terminal domain of the carrier.ConclusionBiochemical characteristics suggest that plant APCs can mediate net transport of adenine nucleotides and hence, like their pendants from animals and yeast, might be involved in the alteration of the mitochondrial adenine nucleotide pool. Although, ATP-Ca was identified as an apparent import substrate of plant APCs in vitro it is arguable whether ATP-Ca formation and thus the corresponding transport can take place in vivo.

【 授权许可】

CC BY   
© Lorenz et al. 2015