Metal binding by citrus dehydrin with histidine-rich domains

Abstract

Dehydrins are hydrophilic proteins that are responsive to osmotic stress, such as drought, cold, and salinity in plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, their functions are not fully understood. Citrus dehydrin, which accumulates mainly in response to cold stress, enhances cold tolerance in transgenic tobacco by reducing lipid peroxidation. It has been demonstrated that citrus dehydrin scavenges hydroxyl radicals. In this study, the metal binding of citrus dehydrin is reported and the specific domain responsible is identified. The metal binding property of citrus dehydrin was tested using immobilized metal ion affinity chromatography (IMAC). Fe3+, Co2+, Ni2+, Cu2+, and Zn2+ bound to citrus dehydrin, but Mg2+, Ca2+, and Mn2+ did not. Among the bound metals, the highest affinity was detected for Cu(2+)-dehydrin binding, which showed a dissociation constant of 1.6 microM. Citrus dehydrin was able to bind up to 16 Cu2+ ions. IMAC indicated that His residues contributed to Cu(2+)-dehydrin binding. The amino acid sequence of CuCOR15 was divided into five domains, of which domain 1 bound Cu2+ most strongly. One portion of domain 1, HKGEHHSGDHH, was the core sequence for the binding. These results suggest that citrus dehydrin binds metals using a specific sequence containing His. Since citrus dehydrin is a radical-scavenging protein, it may reduce metal toxicity in plant cells under water-stressed conditions.

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

“…For example, the Citrus unshiu CuCOR19 DHN protein binds Cu 2+ ions and scavenges reactive oxygen species, presumably to protect membranes from oxidative damage caused by water deficit (Hara et al, 2003(Hara et al, , 2005. 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).…”

“…On the basis of compositional and biophysical properties and their link to abiotic stresses, several functions of DHNs have been proposed, including ion sequestration (Roberts et al, 1993), water retention (McCubbin et al, 1985), and stabilization of membranes or proteins (Close, 1996(Close, , 1997. Observations from in vitro experiments include DHN binding to lipid vesicles (Koag et al, 2003;Kovacs et al, 2008) or metals (Svensson et al, 2000;Heyen et al, 2002;Kruger et al, 2002;Alsheikh et al, 2003;Hara et al, 2005), protection of membrane lipid against peroxidation (Hara et al, 2003), retention of hydration or ion sequestration (Bokor et al, 2005;Tompa et al, 2006), and chaperone activity against the heat-induced inactivation and aggregation of various proteins (Kovacs et al, 2008).…”

Role of plant dehydrins in antioxidation mechanisms

“…However, plant dehydrins contain a much higher proportion of His. For example, the range of His content in ten Arabidopsis dehydrins and dehydrin-like proteins was 3.2% to 13.5% (Hara et al 2005). The proportion of His in several metal-binding dehydrins is described in Table 2.…”

CRISPR-induced null alleles show that Frost protects Drosophila melanogaster reproduction after cold exposure

“…re-establishing ion homeostasis), such that Fst-null flies must trade-off energy allocation to the ovaries with the energy demands of repair and recovery elsewhere in the fly. FST is an intrinsically disordered stress-response protein, a group of proteins that fulfill a diverse range of functions, including protecting membranes from cold stress (Clarke et al, 2015) and binding ions (Hara et al, 2005). Therefore, FST could affect recovery from cold exposure in a variety of ways, including direct or indirect impacts on the ovaries; the fertility and number of eggs laid post-cold; longevity of cold-exposed flies; and performance of the offspring.…”