Interplay of Structural Disorder and Short Binding Elements in the Cellular Chaperone Function of Plant Dehydrin ERD14

Abstract

Details of the functional mechanisms of intrinsically disordered proteins (IDPs) in living cells is an area not frequently investigated. Here, we dissect the molecular mechanism of action of an IDP in cells by detailed structural analyses based on an in-cell nuclear magnetic resonance experiment. We show that the ID stress protein (IDSP) A. thaliana Early Response to Dehydration (ERD14) is capable of protecting E. coli cells under heat stress. The overexpression of ERD14 increases the viability of E. coli cells from 38.9% to 73.9% following heat stress (50 °C × 15 min). We also provide evidence that the protection is mainly achieved by protecting the proteome of the cells. In-cell NMR experiments performed in E. coli cells show that the protective activity is associated with a largely disordered structural state with conserved, short sequence motifs (K- and H-segments), which transiently sample helical conformations in vitro and engage in partner binding in vivo. Other regions of the protein, such as its S segment and its regions linking and flanking the binding motifs, remain unbound and disordered in the cell. Our data suggest that the cellular function of ERD14 is compatible with its residual structural disorder in vivo.

Cellular Chaperone Function of Intrinsically Disordered Dehydrin ERD14

“…Their categorization is based on the highly conserved segments that can be found in their sequences [6] in different combinations: (i) The Ksegment is an approximately 15 amino acid long conserved lysine-rich motif present in all cold-expressed dehydrins. It can be found in multiple copies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) within a dehydrin and, according to in silico predictions, it tends to adopt an amphipathic α-helix structure [7,8]. Presumably, K-segments can play a role in shaping the interaction with partner molecules, which is supported by our earlier observations [9].…”

“…It can be found in multiple copies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) within a dehydrin and, according to in silico predictions, it tends to adopt an amphipathic α-helix structure [7,8]. Presumably, K-segments can play a role in shaping the interaction with partner molecules, which is supported by our earlier observations [9]. (ii) The S-segment is a serine-rich region that can be phosphorylated, and, in most examples, it is wedged between the K-segments.…”

Multiple copies of a novel amphipathic α-helix forming segment in Physcomitrella patens dehydrin play a key role in abiotic stress mitigation

“…The generally accepted working principle of DHNs is associated with their higher expression under stress conditions and interaction with their partner molecules to function as a molecular chaperone ( 17 ). According to the hypothesis by Ingram and Bartels, several K-segments, when present in α-helical conformation, might form intermolecular homobundles ( 20 ).…”

“…According to the hypothesis by Ingram and Bartels, several K-segments, when present in α-helical conformation, might form intermolecular homobundles ( 20 ). In addition to the DHN–DHN interaction, DHNs can also participate in nonspecific interactions with other cellular target proteins to protect the latter from stress-mediated aggregation ( 17 ). DHNs are capable of interacting with partly dehydrated surfaces of various other proteins.…”

“…Arabidopsis DHNs (ERD10 and ERD14) are also known to exhibit protection against thermal aggregation in vitro ( 16 ). Elaborating on the details of the functional mechanism under heat stress, it was concluded that the protection was mainly achieved through protection of the cellular proteome owing to the chaperonic activity of ERD14 via multimer formation ( 17 ).…”