A 42-Kilodalton Annexin-Like Protein Is Associated with Plant Vacuoles

Seals, Darren F.; Parrish, Mitchell; Randall, Stephen K.

doi:10.1104/pp.106.4.1403

Cited by 28 publications

(30 citation statements)

References 41 publications

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“…We have also compared calcium-binding activity (on ligand blots) with a vacuolar annexin protein, VCaB42 Randall, 1994, 1997). Although the vacuolar annexin binds calcium in the native state, with an apparent dissociation constant (K d ) of 60 nm (Seals and Randall, 1994), it does not bind calcium by the calcium ligand-blot assay (Fig. 8).…”

Section: Phosphorylation Of Vcab45 and Calcium-binding Propertiesmentioning

confidence: 99%

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The Calcium-Binding Activity of a Vacuole-Associated, Dehydrin-Like Protein Is Regulated by Phosphorylation

et al. 2002

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A vacuole membrane-associated calcium-binding protein with an apparent mass of 45 kD was purified from celery (Apium graveolens). This protein, VCaB45, is enriched in highly vacuolate tissues and is located within the lumen of vacuoles. Antigenically related proteins are present in many dicotyledonous plants. VCaB45 contains significant amino acid identity with the dehydrin family signature motif, is antigenically related to dehydrins, and has a variety of biochemical properties similar to dehydrins. VCaB45 migrates anomalously in sodium dodecyl sulfate-polyacrylamide gel electrophoresis having an apparent molecular mass of 45 kD. The true mass as determined by matrix-assisted laser-desorption ionization time of flight was 16.45 kD. VCaB45 has two characteristic dissociation constants for calcium of 0.22 Ϯ 0.142 mm and 0.64 Ϯ 0.08 mm, and has an estimated 24.7 Ϯ 11.7 calcium-binding sites per protein. The calcium-binding properties of VCaB45 are modulated by phosphorylation; the phosphorylated protein binds up to 100-fold more calcium than the dephosphorylated protein. VCaB45 is an "in vitro" substrate of casein kinase II (a ubiquitous eukaryotic kinase), the phosphorylation resulting in a partial activation of calcium-binding activity. The vacuole localization, calcium binding, and phosphorylation of VCaB45 suggest potential functions.The vacuole is a reservoir for calcium (Machlon, 1984) and consequently plays an important role in calcium homeostasis (Miller et al., 1990;Allen and Sanders, 1995;Sanders et al., 1999). Regulation of vacuole calcium levels is complex involving a variety of calcium channels and pumps (Sanders et al., 1999;Sze et al., 2000). Sustained elevated levels of cytosolic calcium can be toxic (Hepler and Wayne, 1985), so under normal conditions, cytosolic calcium levels increase only transiently. Proteinaceous calcium buffers may serve as homeostats to attenuate the signal transduction system. Well-characterized protein calcium buffers include calreticulin and calsequestrin (Ostwald and MacLennon, 1974;Campbell et al., 1983b). Homologs of calsequestrin (Krause et al., 1989;Xing et al., 1994), calreticulin (Chen et al., 1994;Napier et al., 1995;Nelson et al., 1997), and calnexin (Li et al., 1998) have been identified in plants. These calcium-binding proteins can bind on the order of 20 to 50 calcium ions with both high-(1-3 sites per protein) and low-(20-50 sites per protein) affinity sites. The levels of calcium binding proteins may have a significant impact on signaling processes and may regulate second messenger transmission (Camacho and Lechleiter, 1995;Mery et al., 1996;Coppolino et al., 1997). In an alternative role, calcium-dependent interactions of calnexin and calreticulin have been characterized with a variety of proteins (Nigam et al., 1994;Peterson et al., 1995) and both are implicated in the promotion of correct protein folding (Hebert et al., 1996). These latter activities clearly suggest a molecular chaperone role. Recently, a high-capacity, low-affinity calcium-binding protei...

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Section: Phosphorylation Of Vcab45 and Calcium-binding Propertiesmentioning

confidence: 99%

“…VCaB45 binds calcium in the ligand blot but the vacuole annexin, VCaB42, does not. VCaB42 was obtained as previously described (Seals and Randall, 1994) and loaded in the first lane of each gel. VCaB45 was eluted from a nitrocellulose spot cut from a two-dimensional gel.…”

Section: Fractionation Of Triton X-100 Supernatant (Lumenal Vacuolar mentioning

confidence: 99%

The Calcium-Binding Activity of a Vacuole-Associated, Dehydrin-Like Protein Is Regulated by Phosphorylation

et al. 2002

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“…On the other hand, there are annexins (like Drosophila annexin IX and X, Hydra annexin XII) that appear to be specific for the individual species (Johnston et al, 1990;Schlaepfer et al, 1992). There are also indications for the existence of unique plant-specific annexins (Seals et al, 1994;Smallwood et al, 1990). However, annexins do not seem entirely ubiquitous as annexinlike coding sequences have not been identified in the Saccharomyces cerevisiae genome, and they have not been found in protozoa and prokaryotes.…”

Section: Introductionmentioning

confidence: 99%

Immunolocalization of a novel annexin‐like protein encoded by a stress and abscisic acid responsive gene in alfalfa

et al. 1998

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SummaryWe report here on the isolation and characterization of a full-length cDNA clone from alfalfa termed AnnMs2 encoding a 333 amino acid long polypeptide that shows 32-37% sequence identity with both mammalian and plant annexins, and has four tandem repeats. While other plant annexins exhibit a high level of sequence similarity to each other (up to 77% identity at amino acid level), AnnMs2 appears to be a distinct type of plant annexins. All the four endonexin folds contain the conserved eukaryotic motif within this alfalfa protein, but this element is considerably different in the second repeat. The AnnMs2 gene is expressed in various tissues of alfalfa with elevated mRNA accumulation in root and flower. This gene is activated in cells or tissues exposed to osmotic stress, abscisic acid (ABA) or water deficiency. The recombinant AnnMs2 protein is able to bind to phospholipid in the presence of Ca 2ϩ . Indirect immunofluorescence studies using affinity purified rabbit anti-AnnMs2 peptide antibody show mainly nucleolar localization, but the protein sequence lacks the usual nuclear localization signal. The potential role of this novel annexin-like protein in the basic and stress-induced cellular functions is discussed.

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“…However, at the present stage any conclusion about the subcellular localization of CR proteins in spinach leaves would be premature. Although in plant cells the vacuole, together with the cell wall (Gilroy et al, 1993;Seals et al, 1994), is generally regarded to be the main site of accumulation of Ca 2+ , there is equal evidence that the ER may play an important role in Ca 2+ homeostasis (Bush et al, 1989. ER-enriched microsomal fractions from celery were shown to contain otherwise uncharacterized Ca 2+ -binding proteins with apparent molecular masses of 55 and 58 kD (Randall, 1992).…”

Section: Discussionmentioning

confidence: 99%