Phosphorylation regulated ion‐binding is a property shared by the acidic subclass dehydrins

Abstract

Dehydrins are a family of proteins that accumulate in response to abiotic stresses. Little is known about the biochemical functions of these proteins. It is known that the Arabidopsis dehydrin, ERD14, is activated by phosphorylation to bind calcium and other ions. To begin to categorize the Arabidopsis dehydrins into functional families, we determined whether representative members of the dehydrin sub families share the properties of ERD14. When phosphorylated in vitro with casein kinase II; recombinant COR47, and ERD10 (and ERD14) become activated to bind calcium. ERD14 exhibited the highest calcium-binding activity followed by ERD10 and COR47. These dehydrins, when isolated from cold-treated Arabidopsis plants were also shown to have phosphorylation-dependent, calciumbinding activity. RAB18 showed very little calcium binding activity, even though it was phosphorylated by casein kinase II. XERO2 was not phosphorylated with CKII and did not bind calcium. Competition studies suggest that other divalent cations may bind to the dehydrins COR47, ERD10, and ERD14. Utilizing matrix-assisted laser desorption ionization -time of flight mass spectroscopy (MALDI-TOF), we determined that the poly serine region located in all three calcium-binding family members (COR47, ERD10, and ERD14) is the most likely phosphorylation site responsible for the activation of calcium binding. These results are consistent with a distinct biochemical function for the acidic subclass of dehydrins (COR47, ERD10, and ERD14) as ion (calcium)-interacting proteins.

Tunable Membrane Binding of the Intrinsically Disordered Dehydrin Lti30, a Cold-Induced Plant Stress Protein

“…Consistent with the predictions, we observe that Lti30 easily becomes phosphorylated by PKC as detected by radiolabeled phosphate (Figure 8). With CKII, we observe no corresponding effect, consistent with previous reports from other groups (Alsheikh et al, 2005). We previously showed that phosphorylation has no detectable effect on the structures of solubilized dehydrins (Mouillon et al, 2008), and, in line with this, CD analysis of Lti30 reveals no structural changes upon phosphorylation (see Supplemental Figure 5 online).…”

“…Comparison of the different phosphorylation sites among the divergent proteins in Table 1 points again at a functional division within the dehydrin family. As demonstrated earlier, the Arabidopsis dehydrins Cor47 and Lti29 (both SK n dehydrins), but not Lti30, become phosphorylated in vitro by CKII (Riera et al, 2004;Alsheikh et al, 2005;Mouillon et al, 2008). The main reason for this different kinase selectivity is the lack of conserved multi-S-segments, which constitute the prime target for CKII activity, in the K n dehydrins, such as Lti30.…”

Chaperone Activity of ERD10 and ERD14, Two Disordered Stress-Related Plant Proteins

“…They can be phosphorylated, which usually results in lower SDS-PAGE mobility. Furthermore, phosphorylation makes these proteins capable of binding bivalent metal ions (Alsheikh et al, 2003(Alsheikh et al, , 2005.…”

“…These functions are usually intimately related to the structural characteristics of these proteins, such as high flexibility, structural adaptability, and extended conformational states. IDPs have been shown to have high ion-binding capacity (Heyen et al, 2002;Alsheikh et al, 2003Alsheikh et al, , 2005Saavedra et al, 2006;, to be able to bind membranes (Danyluk et al, 1998;Ismail et al, 1999a;Koag et al, 2003), and to have both RNA and protein chaperone activity (Tompa and Csermely, 2004). In Arabidopsis, approximately 23% of proteins are predicted to be fully disordered (Oldfield et al, 2005).…”

The K-Segment of Maize DHN1 Mediates Binding to Anionic Phospholipid Vesicles and Concomitant Structural Changes

“…Members of the acidic subgroup of DHNs (ERD14, ERD10, and COR47) were observed to increase Ca 2+ binding when phosphorylated in the poly-Ser motif (Alsheikh et al, 2003). It was also recognized that acidic residues of DHNs are involved in ion binding (Alsheikh et al, 2005). Water deficit can trigger an increase in metal ion concentration, which may cause stress to the plant directly and indirectly.…”