Calmodulin-stimulated Ca2+-ATPases in the Vacuolar and Plasma Membranes in Cauliflower

Askerlund, Per

doi:10.1104/pp.114.3.999

Cited by 41 publications

(22 citation statements)

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“…Calmodulin stimulated ATPase activity by approximately sixfold in a dose-dependent manner, showing a half-maximum activation at ‫01ف‬ nM for SCaM-1 (Figure 9) or bovine calmodulin (not shown). This value represents a higher K 1/2 than that reported for ACA2p (K 1/2 ϭ 30 nM bovine calmodulin), in agreement with prior findings on the biochemical properties of enzymes purified from plant tissues, that is, that Ca 2ϩ pumps from the plasma membrane have a stronger binding affinity for calmodulin than do pumps from the tonoplast (Askerlund, 1996(Askerlund, , 1997 or other endomembranes (Dainese et al, 1997;Bonza et al, 1998). The greater calmodulin binding affinity of SCA1p also might be attributable to the The presence of an N-terminal regulatory domain in SCA1p was demonstrated by an N-terminal deletion that resulted in a calmodulin-independent (i.e., deregulated) pump with kinetic properties similar to those of a full-length pump stimulated by calmodulin.…”

Section: Discussionsupporting

confidence: 78%

“…Second, unlike type IIB pumps from animals, which are thought to be located exclusively in the plasma membrane, the plant isoforms have been found only in non-plasma membrane locations, such as ACA2p in the ER membrane (Hong et al, 1999), BCA1p in the tonoplast (Malmstrom et al, 1997), and ACA1p, which is thought to reside in the chloroplast inner membrane (Huang et al, 1993). Despite the biochemical evidence for a calmodulin-regulated Ca 2 ϩ -ATPase in the plant cell plasma membrane (Evans, 1994;Askerlund, 1997;Dainese et al, 1997;Hwang et al, 1997;Bonza et al, 1998), the corresponding gene for this has not been cloned, and it is not known whether the anticipated pump is more similar to an animal type IIB pump or to the calmodulin-regulated pumps found in plant cell endomembranes.In this article, we report the isolation and characterization of a gene, SCA1 (for soybean Ca 2 ϩ -ATPase 1), encoding a calmodulin-regulated Ca 2 ϩ -ATPase that is located at the plasma membrane in soybean cells. Both biochemical and genetic evidence demonstrate that SCA1p has an N-terminal calmodulin-regulated autoinhibitor.…”

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Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane

et al. 2000

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Ca 2 ؉ -ATPases are key regulators of Ca 2 ؉ ion efflux in all eukaryotes. Animal cells have two distinct families of Ca 2 ؉ pumps, with calmodulin-stimulated pumps (type IIB pumps) found exclusively at the plasma membrane. In plants, no equivalent type IIB pump located at the plasma membrane has been identified at the molecular level, although related isoforms have been identified in non-plasma membrane locations. Here, we identify a plant cDNA, designated SCA1 (for soybean Ca 2 ؉ -ATPase 1), that encodes Ca 2 ؉ -ATPase and is located at the plasma membrane. The plasma membrane localization was determined by sucrose gradient and aqueous two-phase membrane fractionations and was confirmed by the localization of SCA1p tagged with a green fluorescent protein. The Ca 2 ؉ -ATPase activity of the SCA1p was increased approximately sixfold by calmodulin ( K 1/2 ‫ف‬ 10 nM). Two calmodulin binding sequences were identified in the N-terminal domain. An N-terminal truncation mutant that deletes sequence through the two calmodulin binding sites was able to complement a yeast mutant (K616) that was deficient in two endogenous Ca 2 ؉ pumps. Our results indicate that SCA1p is structurally distinct from the plasma membrane-localized Ca 2 ؉ pump in animal cells, belonging instead to a novel family of plant type IIB pumps found in multiple subcellular locations. In plant cells from soybean, expression of this plasma membrane pump was highly and rapidly induced by salt (NaCl) stress and a fungal elicitor but not by osmotic stress. INTRODUCTIONCa 2 ϩ plays a central role as a second messenger in signal transduction of all eukaryotes (Bootman and Berrige, 1995;Clapham, 1995). The transient increase of cytosolic free Ca 2 ϩ concentration, [Ca 2 ϩ ] cyt , is correlated with a variety of external signals such as touch, temperature shift, abscisic acid, auxin, red light, fungal elicitors, salinity/drought, anoxia, gravity, gibberellic acid, cytokinin, oxidative stress, and hypoxia (Bush, 1995; Sanders et al., 1999). In turn, the increased [Ca 2 ϩ ] cyt triggers many signal transduction pathways, including the regulation of enzyme activity, ion channel activity, and gene expression, which results in diverse cellular responses (Bush, 1995). In addition to its role as a second messenger, Ca 2 ϩ also is important in regulating the processing of proteins in secretory pathways (Rudolph et al., 1989). Thus, cells require carefully regulated transport systems to control [Ca 2 ϩ ] in the cytoplasm and endomembrane compartments. Influx of Ca 2 ϩ to the cytosol occurs as a "downhill" transport through Ca 2 ϩ channels (Sanders et al., 1999). In contrast, the efflux of Ca 2 ϩ from the cytosol is mediated by two active Ca 2 ϩ transporters-Ca 2 ϩ pumps and Ca 2 ϩ /H ϩ antiporters-which are powered by ATP hydrolysis and proton motive force, respectively (Bush, 1995). In plants, Ca 2 ϩ -ATPases are believed to be a major Ca 2 ϩ transporter for the endoplasmic reticulum (ER), Golgi apparatus, vacuole, plastid inner membrane, and plasma membrane (Sander...

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Section: Discussionsupporting

confidence: 78%

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confidence: 99%

Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane

et al. 2000

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“…The N terminus was shown to interact with mCaM in a Ca 2ϩ -dependent manner (20), and the activity of the protein was stimulated by mCaM in vitro (21). In the present work, we have studied the interactions of a peptide corresponding to the CaM-binding domain of BCA1 (CATPp) with the most conserved and most divergent CaM isoforms from soybean, SCaM-1, and SCaM-4 respectively.…”

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confidence: 99%

Structurally Homologous Binding of Plant Calmodulin Isoforms to the Calmodulin-binding Domain of Vacuolar Calcium-ATPase

Yamniuk

Vogel

2004

Journal of Biological Chemistry

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The discovery that plants contain multiple calmodulin (CaM) isoforms having variable sequence identity to mammalian CaM has sparked a flurry of new questions regarding the intracellular role of Ca 2؉ regulation in plants. To date, the majority of research in this field has focused on the differential enzymatic regulation of various mammalian CaM-dependent enzymes by the different plant CaM isoforms. However, there is comparatively little information on the structural recognition of target enzymes found exclusively in plant cells. Here we have used a variety of spectroscopic techniques, including nuclear magnetic resonance, circular dichroism, and fluorescence spectroscopy, to study the interactions of the most conserved and most divergent CaM isoforms from soybean, SCaM-1, and SCaM-4, respectively, with a synthetic peptide derived from the CaM-binding domain of cauliflower vacuolar calcium-ATPase. Despite their sequence divergence, both SCaM-1 and SCaM-4 interact with the calcium-ATPase peptide in a similar calciumdependent, stoichiometric manner, adopting an antiparallel binding orientation with an ␣-helical peptide. The single Trp residue is bound in a solvent-inaccessible hydrophobic pocket on the C-terminal domain of either protein. Thermodynamic analysis of these interactions using isothermal titration calorimetry demonstrates that the formation of each calcium-SCaM-calcium-ATPase peptide complex is driven by favorable binding enthalpy and is very similar to the binding of mammalian CaM to the CaM-binding domains of myosin light chain kinases and calmodulin-dependent protein kinase I.

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“…Second, some plant isoforms have been found in non-plasma membrane locations, such as ACA2 (endoplasmic reticulum) (13), and BCA1 (tonoplast) (14). Despite these differences, biochemical and genetic studies on ACA2 and BCA1 suggest mechanisms of autoinhibition and calmodulin activation that are analogous to a PMCA (12,(15)(16)(17).…”

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Autoinhibition of a Calmodulin-dependent Calcium Pump Involves a Structure in the Stalk That Connects the Transmembrane Domain to the ATPase Catalytic Domain

Curran¹,

Hwang²,

Corbin³

et al. 2000

Journal of Biological Chemistry

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The regulation of Ca 2؉ -pumps is important for controlling [Ca 2؉ ] in the cytosol and organelles of all eukaryotes. Here, we report a genetic strategy to identify residues that function in autoinhibition of a novel calmodulin-activated Ca 2؉ -pump with an N-terminal regulatory domain (isoform ACA2 from Arabidopsis). Mutant pumps with constitutive activity were identified by complementation of a yeast (K616) deficient in two Ca 2؉ -pumps. Fifteen mutations were found that disrupted a segment of the N-terminal autoinhibitor located between Lys 23 and Arg 54 . Three mutations (E167K, D219N, and E341K) were found associated with the stalk that connects the ATPase catalytic domain (head) and with the transmembrane domain. Enzyme assays indicated that the stalk mutations resulted in calmodulin-independent activity, with V max , K mATP , and K mCa 2؉ similar to that of a pump in which the N-terminal autoinhibitor had been deleted. A highly conservative substitution at Asp 219 (D219E) still produced a deregulated pump, indicating that the autoinhibitory structure in the stalk is highly sensitive to perturbation. In plasma membrane H ؉ -ATPases from yeast and plants, similarly positioned mutations resulted in hyperactive pumps. Together, these results suggest that a structural feature of the stalk is of general importance in regulating diverse Ptype ATPases.

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Calmodulin-stimulated Ca2+-ATPases in the Vacuolar and Plasma Membranes in Cauliflower

Cited by 41 publications

References 43 publications

Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane

Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane

Structurally Homologous Binding of Plant Calmodulin Isoforms to the Calmodulin-binding Domain of Vacuolar Calcium-ATPase

Autoinhibition of a Calmodulin-dependent Calcium Pump Involves a Structure in the Stalk That Connects the Transmembrane Domain to the ATPase Catalytic Domain

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Calmodulin-stimulated Ca2+-ATPases in the Vacuolar and Plasma Membranes in Cauliflower

Cited by 41 publications

References 43 publications

Identification of a Calmodulin-Regulated Soybean Ca2+-ATPase (SCA1) That Is Located in the Plasma Membrane

Identification of a Calmodulin-Regulated Soybean Ca2+-ATPase (SCA1) That Is Located in the Plasma Membrane

Structurally Homologous Binding of Plant Calmodulin Isoforms to the Calmodulin-binding Domain of Vacuolar Calcium-ATPase

Autoinhibition of a Calmodulin-dependent Calcium Pump Involves a Structure in the Stalk That Connects the Transmembrane Domain to the ATPase Catalytic Domain

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Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane

Identification of a Calmodulin-Regulated Soybean Ca²⁺-ATPase (SCA1) That Is Located in the Plasma Membrane