Identification of a Calmodulin-Regulated Ca2+-ATPase in the Endoplasmic Reticulum1
- 1 April 1999
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 119 (4), 1165-1176
- https://doi.org/10.1104/pp.119.4.1165
Abstract
A unique subfamily of calmodulin-dependent Ca2+-ATPases was recently identified in plants. In contrast to the most closely related pumps in animals, plasma membrane-type Ca2+-ATPases, members of this new subfamily are distinguished by a calmodulin-regulated autoinhibitor located at the N-terminal instead of a C-terminal end. In addition, at least some isoforms appear to reside in non-plasma membrane locations. To begin delineating their functions, we investigated the subcellular localization of isoform ACA2p (ArabidopsisCa2+-ATPase, isoform 2 protein) in Arabidopsis. Here we provide evidence that ACA2p resides in the endoplasmic reticulum (ER). In buoyant density sucrose gradients performed with and without Mg2+, ACA2p cofractionated with an ER membrane marker and a typical “ER-type” Ca2+-ATPase, ACA3p/ECA1p. To visualize its subcellular localization, ACA2p was tagged with a green fluorescence protein at its C terminus (ACA2-GFPp) and expressed in transgenic Arabidopsis. We collected fluorescence images from live root cells using confocal and computational optical-sectioning microscopy. ACA2-GFPp appeared as a fluorescent reticulum, consistent with an ER location. In addition, we observed strong fluorescence around the nuclei of mature epidermal cells, which is consistent with the hypothesis that ACA2p may also function in the nuclear envelope. An ER location makes ACA2p distinct from all other calmodulin-regulated pumps identified in plants or animals.Keywords
This publication has 51 references indexed in Scilit:
- A calcium pump at the higher plant nuclear envelope?FEBS Letters, 1998
- A calmodulin‐stimulated Ca2+‐ATPase from plant vacuolar membranes with a putative regulatory domain at its N‐terminus1FEBS Letters, 1997
- Covisualization by computation optical-sectioning microscopy of integrin and associated proteins at the cell membrane of living onion protoplastsProtoplasma, 1996
- A Single Gene May Encode Differentially Localized Ca 2+ -ATPases in TomatoPlant Cell, 1996
- BiP (GRP78), an essential hsp70 resident protein in the endoplasmic reticulumCellular and Molecular Life Sciences, 1994
- Protein sorting to the vacuolar membrane.Plant Cell, 1992
- The sarcoplasmic reticulum Ca2+-ATPase, SERCA1a, contains endoplasmic reticulum targeting informationBiochemical and Biophysical Research Communications, 1992
- [34] Chlorophylls and carotenoids: Pigments of photosynthetic biomembranesPublished by Elsevier ,1987
- Purification of the proton pumping ATPase from plant plasma membranesBiochemical and Biophysical Research Communications, 1984
- Triton-stimulated nucleoside diphosphatase activity: Subcellular localization in corn root homogenatesProtoplasma, 1982