Plant Ca2+-ATPases

Abstract

Plant Phys i ol ogy De part ment, In sti tute of Plant Bi ol ogy, Wrocław Uni ver sity, Ab stractPlant cal cium pumps, sim i larly to an i mal Ca 2+ pumps, be long to the superfamily of P-type ATPases com pris ing also the plasma mem brane H + -ATPase of fungi and plants, Na + /K + ATPase of an i mals and H + /K + ATPase of mam ma lian gas tric mu cosa. Ac cord ing to their sen si tiv ity to calmodulin the plant Ca 2+ -ATPases have been di vided into two sub groups: type IIA (homo logues of an i mal SERCA) and type IIB (homo logues of an i mal PMCA). Re gard less of the sim i lar i ties in a pro tein sequence, the plant Ca 2+ pumps dif fer from those in an i mals in their cel lu lar lo cal iza tion, struc ture and sen si tiv ity to in hib itors. Genomic in ves ti ga tions re vealed mul ti plic ity of plant Ca 2+ -ATPases; they are pres ent not only in the plasma membranes and ER but also in mem branes of most of the cell compart ments, such as vac u ole, plas tids, nu cleus or Golgi ap pa ratus. Stud ies us ing yeast mu tants made pos si ble the func tional and bio chem i cal char ac ter iza tion of in di vid ual plant Ca 2+ --ATPases. Plant cal cium pumps play an es sen tial role in sig nal transduction path ways, they are re spon si ble for the reg u la tion of [Ca 2+ ] in both cy to plasm and endomembrane com partments. These Ca 2+ -ATPases ap pear to be in volved in plant ada p ta tion to stress con di tions, like sa lin ity, chill ing or an oxia. List of ab bre vi a tions:ACA, autoinhibited Ca 2+ -ATPase; CaM, calmodulin; CDPK, Ca 2+ -de pend ent pro tein kinase; CPA, cyclopiazonic acid; [Ca 2+ ] cyt , cytosolic calcium con cen tra tion; EB, erythrosin B; ECA, ER-type Ca 2+ -ATPase; ER, endoplasmic re tic ulum; FITC, fluorescein isothiocyanate; NE, nu clear en ve lope; PKC, pro tein kinase C; PLN, phospholamban; PM, plasma mem brane; PMCA, plasma mem brane Ca 2+ -ATPase; P-type ATPase, ATPase form ing phosphoenzyme; SER, sarcoplasmic/ /endoplasmic re tic u lum; SERCA, sarcoplasmic/endoplasmic re tic u lum Ca 2+ -ATPase; TG, thapsigargin In tro duc tionThe cru cial func tion of cal cium ions in the reg u la tion of me tab o lism and de vel op ment of eukaryotic or ganisms is well es tab lished. Ca 2+ is re quired for the protein sort ing in se cre tory sys tem as well as for pro tein sta bil ity and ac tiv ity (Hong et al. 1999). Espe cially its role as a sec ond messenger cou pling extracellular stim uli to the spe cific cell re sponses is widely recog nized. In the cytosol of plant cells, Ca 2+ con centra tion is main tained at the submicro molar lev els, 0.2-0.6 µmol·dm -3 (Hwang et al. 1997). Many abiotic and bi otic stim uli in clud ing sa lin ity, cold, drought, light, touch, plant hor mones, fun gal elicitors or nodulation fac tors may cause the transient in crease in cy to plas mic Ca 2+ (Knight et al. 1997, Olbe et al. 1997, Sanders et al. 2002. Changes in [Ca 2+ ] cyt arise from Ca 2+ en try into cyto plasm through cal cium chan nels pres ent in both the plasma mem brane and intracellular mem brane...

Arabidopsis ACA7, encoding a putative auto-regulated Ca2+-ATPase, is required for normal pollen development

“…ATPases family in Arabidopsis. This family encompasses ten members and only few have been characterized at the functional level (Kabała and Kłobus 2005;Boursiac and Harper 2007). Protein sequence analysis showed that ACA7 presented the characteristic domains conserved across the ACA family, including the N-terminal calmodulin sensor domain that regulates the activity of this family of Ca 2?…”

“…ACA proteins are part of the PIIB type of Ca 2? -ATPases, with ten members in Arabidopsis (Kabała and Kłobus 2005). They all present a calmodulin-regulated autoinhibitory domain and show nearly 50% protein sequence identity with animal plasma membrane type (PM-type) Ca 2?…”

“…They all present a calmodulin-regulated autoinhibitory domain and show nearly 50% protein sequence identity with animal plasma membrane type (PM-type) Ca 2? pumps (Kabała and Kłobus, 2005;Boursiac and Harper 2007). Some members of this family of Ca 2?…”

ACA12 is a deregulated isoform of plasma membrane Ca2+-ATPase of Arabidopsis thaliana

“…In previously characterized members of the ACA subgroup, the N-terminus has been found to have an auto-inhibitory domain and a partially overlapping high affinity calmodulin (CaM) binding site (Geisler et al 2000a; Baxter et al 2003; Kabala and Klobus 2005; Boursiac and Harper 2007; Bonza and De Michelis 2011; Pedersen et al 2012); a second low affinity CaM-binding site has been recently identified just 8 aa downstream the first one in ACA8, one of the best characterized ACA isoform (Tidow et al 2012). In all ACA isoforms characterized so far, CaM-binding suppresses the auto-inhibitory action of the N-terminus, increasing V max and decreasing K 0.5 for free Ca 2+ .…”

The Solution Structure of a Plant Calmodulin and the CaM-binding Domain of the Vacuolar Calcium-ATPase BCA1 Reveals a New Binding and Activation Mechanism

“…For example, ACA2 and ACA4 are located at the endoplasmic reticulum and the prevacuolar membrane, respectively, whereas ACA8 and ACA9 are located on the plasma membrane (15; reviewed in Refs. 16,17). The BCA1 protein is a type IIB Ca 2ϩ -ATPase with a vacuolar localization that was discovered in the plant Brassica oleracea (cauliflower) (18).…”