Identification of a calmodulin-regulated Ca[sup 2+]-ATPase in the endoplasmic reticulum

Journal Article · Thu Apr 01 00:00:00 EST 1999 · Plant Physiology; (Bethesda)

DOI:https://doi.org/10.1104/pp.119.4.1165· OSTI ID:6333322

Hong, B; Wang, Y; Harper, J F ^[1]; Ichida, A; Gens, J S; Pickard, B G ^[2]

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1. Scripps Research Inst., La Jolla, CA (United States). Dept. of Cell Biology
2. Washington Univ., St. Louis, MO (United States). Dept. of Biology

A unique subfamily of calmodulin-dependent Ca[sup 2+]-ATPases was recently identified in plants. In contrast to the most closely related pumps in animals, plasma membrane-type Ca[sup 2+]-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, the authors investigated the subcellular localization of isoform ACA2p (Arabidopsis Ca[sup 2+]-ATPase, isoform 2 protein) in Arabidopsis. Here they provide evidence that ACA2p resides in the endoplasmic reticulum (ER). In buoyant density sucrose gradients performed with and without MG[sup 2+], ACA2p cofractionated with an ER membrane marker and a typical ER-type Ca[sup 2+]-ATPase, ACA3p/ECA1p. To visualize its subcellular localization, ACA2p was tagged with a green fluorescence protein at its C terminus (ACA2-GFP[sub p]) and expressed in transgenic Arabidopsis. The authors collected fluorescence images from live root cells using confocal and computational optical-sectioning microscopy. ACA2-GFP[sub p] appeared as a fluorescent reticulum, consistent with an ER location. In addition, they 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.

• OSTI ID: 6333322
• Journal Information: Plant Physiology; (Bethesda), Vol. 119:4; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ATP-ASE
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL LOCALIZATION
CALMODULIN
CELL MEMBRANES
ENDOPLASMIC RETICULUM
PLANTS
SUBCELLULAR DISTRIBUTION
ACID ANHYDRASES
CELL CONSTITUENTS
DISTRIBUTION
ENZYMES
HYDROLASES
KINETICS
MEMBRANES
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
PROTEINS
REACTION KINETICS
550200* - Biochemistry