Disease relevance of CAM1

• Expression of a subclone of amino acids 482-702 in Escherichia coli generated a peptide that bound CaM [1].
• Using the Bordetella pertussis calmodulin-dependent adenylate cyclase reporter fusion system, we provide direct biochemical evidence that five R. solanacearum effector proteins are translocated into plant host cells through the TTSS [2].
• Here we report the characterization of a tomato gene (APR134) encoding a CaM-related protein that is induced in disease-resistant leaves in response to attack by Pseudomonas syringae pv. tomato [3].

High impact information on CAM1

• Sequenced regions of TCH 2 and TCH 3 contain 44% and 70% amino acid identities to calmodulin, respectively [4].
• The regulation of this calmodulin-related gene family in Arabidopsis suggests that calcium ions and calmodulin are involved in transduction of signals from the environment, enabling plants to sense and respond to environmental changes [4].
• Recent genetic evidence has revealed isoform-specific functions for a CDPK that is essential for Plasmodium berghei gametogenesis, and for a related chimeric Ca(2+) and calmodulin-dependent protein kinase (CCaMK) that is essential to the formation of symbiotic nitrogen-fixing nodules in plants [5].
• HRB1 and all other family members contain a ZZ-type zinc finger domain, which in other organisms is implicated in protein-protein interactions between dystrophin and calmodulin and between transcriptional adaptors and activators [6].
• DRL1 is a putative ATP/GTP binding protein; in addition, calmodulin binding activity was demonstrated in vitro for the C terminus of the DRL1 protein [7].

Biological context of CAM1

• The conceptual TCH3 product is 58 to 60% identical to known Arabidopsis calmodulins; however, unlike calmodulin, which has four Ca2+ binding sites, TCH3 has six potential Ca2+ binding domains [8].
• The gene product, TCH2, belongs to the calmodulin (CaM) family of proteins and contains four highly conserved Ca(2+)-binding EF-hands [9].
• Touch-inducible genes for calmodulin and a calmodulin-related protein are located in tandem on a chromosome of Arabidopsis thaliana [10].
• The UV-A/blue light induction of CHS expression does not appear to involve calmodulin, whereas the UV-B response does; this difference indicates that the signal transduction pathways are, at least in part, distinct [11].
• These results are consistent with the idea that a Ca(2+)-mediated signalling pathway eliciting some changes in gene expression may consist of CaM, or a structurally related Ca2+ binding protein, and transcription factors [12].

Anatomical context of CAM1

• A Ca(2+)-ATPase was purified from plasma membranes (PM) isolated from Arabidopsis cultured cells by calmodulin (CaM)-affinity chromatography [13].
• Residues influencing CaM negatively are situated on the other face of the helix, likely to face the cytosol, whereas residues controlling CaM binding positively are scattered throughout [14].
• In the presence of calcium and calmodulin, AtKCBP no longer binds microtubules to the coverslip surface [15].
• Vacuolar Na+/H+ antiporter cation selectivity is regulated by calmodulin from within the vacuole in a Ca2+- and pH-dependent manner [16].
• Calmodulin, a highly conserved protein family that has long been well known as an intracellular calcium sensor, was identified in the culture medium and cell walls of Arabidopsis thaliana suspension-cultured cells by immunoblotting assay [17].

Associations of CAM1 with chemical compounds

• Molecular and biochemical evidence for the involvement of calcium/calmodulin in auxin action [18].
• The CaM antagonist N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide hydrochloride inhibited the auxin-induced cell elongation but not the auxin-induced expression of ZmSAUR1 [18].
• The cDNA encoded protein bound to biotinylated calmodulin and 35S-labeled calmodulin in the presence of calcium and failed to bind in the presence of EGTA, a calcium chelator [19].
• A calcium/calmodulin-binding serine/threonine protein kinase homologous to the mammalian type II calcium/calmodulin-dependent protein kinase is expressed in plant cells [20].
• Quantitative PCR was used to confirm the induction of genes localized in the chloroplast, mitochondria, and plasma membrane, and genes responsive to calcium/calmodulin complexes, ethylene, jasmonate, ethylene biosynthesis, WRKY, and cell death [21].

Physical interactions of CAM1

• CaM overlay assays localized the CaM-binding domain of At-ACA8p to a region of the N terminus of the enzyme around tryptophan-47, in contrast to a C-terminal localization for its animal counterparts [13].
• TCH3 encodes an unusual calcium ion-binding protein that is closely related to calmodulin but has the potential to bind six calcium ions [22].
• Calmodulin isoforms differentially enhance the binding of cauliflower nuclear proteins and recombinant TGA3 to a region derived from the Arabidopsis Cam-3 promoter [12].
• We demonstrate that an IQD1-GFP fusion protein is targeted to the cell nucleus and that recombinant IQD1 binds to calmodulin in a Ca(2+)-dependent fashion [23].
• Molecular genetic analysis using site-directed and deletion mutants revealed that loss of calmodulin binding completely abolished the function of DWF1 in planta, whereas partial loss of calmodulin binding resulted in a partial dwarf phenotype in complementation studies [24].

Regulatory relationships of CAM1

• Furthermore, these results also suggest that calcium/calmodulin-regulated protein phosphorylation involving CRCK1 plays a role in stress signal transduction in plants [25].
• Our results show that the root-specific calcium/calmodulin-regulated GAD1 plays a major role in GABA synthesis in plants under normal growth conditions and in response to stress [26].
• A calmodulin-stimulated Ca2+-ATPase from plant vacuolar membranes with a putative regulatory domain at its N-terminus [27].
• This contrasts strikingly with the requirement of calmodulin for in vitro motility of brush border myosin I. Calmodulin could regulate AtKCBP binding to microtubules in the cell by inhibiting the binding of the motor to microtubules [15].
• Response to darkness of late-responsive dark-inducible genes is positively regulated by leaf age and negatively regulated by calmodulin-antagonist-sensitive signalling in Arabidopsis thaliana [28].

Other interactions of CAM1

• At-ACA8 encodes a plasma membrane-localized calcium-ATPase of Arabidopsis with a calmodulin-binding domain at the N terminus [13].
• The enzymatic activities of the pure recombinant GAD1 and GAD2 proteins were stimulated 35- and 13-fold, respectively, by Ca2+/calmodulin but not by Ca2+ or calmodulin alone [29].
• CRCK1 does not show high homology to calcium/calmodulin-dependent protein kinases in animals [25].
• Chemical crosslinking of 35S-labeled calmodulin to protoplasts revealed 117- and 41-kDa plasma membrane proteins specifically bound to calmodulin, whereas cross-linking with intact suspension-cultured cells verified more calmodulin binding proteins which might be cell wall-associated in addition to membrane-localized [17].
• Structural features of some plant motors suggest calcium, through calmodulin, is likely to play a key role in regulating the function of both microtubule- and actin-based motors in plants [30].

Analytical, diagnostic and therapeutic context of CAM1

• A synthetic peptide of amino acids 20-45, corresponding to the potential CaM binding region, was used for calcium-dependent mobility shift assays [18].
• The cDNA designated as ZmSAUR1 (Zea mays SAURs) was expressed in Escherichia coli, and the recombinant protein was purified by CaM affinity chromatography [18].
• Sequence analysis of 77 positive clones that interact with CaM in a Ca(2+)-dependent manner revealed 20 CBPs, including 14 previously unknown CBPs [31].
• Genomic southern blot suggests that Bryonia calmodulin is encoded by a single-copy gene [32].
• Such disulfide-stabilized peptides represent useful models to engineer metal specificity in new calmodulin proteins, facilitating the development of new systems to monitor metal pollution in biosensors and to increase metal binding capability of bacterial and plant cells in bioremediation techniques [33].

References