Membrane-induced folding of the plant-stress protein Lti30.

Abstract

Dehydrins are disordered proteins that are expressed in plants as a response to embryogenesis and water-related stress. The molecular function and structural action of the dehydrins are yet elusive, but increasing evidence points to a role in protecting the structure and functional dynamics of cell membranes. An intriguing example is the cold-induced dehydrin Lti30 that binds to membranes by its conserved K segments. Moreover, this binding can be regulated by pH and phosphorylation and shifts the membrane phase transition to lower temperatures, consistent with the protein's postulated function in cold stress. In this study, we reveal how the Lti30-membrane interplay works structurally at atomic level resolution in Arabidopsis (Arabidopsis thaliana). Nuclear magnetic resonance analysis suggests that negatively charged lipid head groups electrostatically capture the protein's disordered K segments, which locally fold up into a-helical segments on the membrane surface. Thus, Lti30 conforms to the general theme of structure-function relationships by folding upon binding, in spite of its disordered, atypically hydrophilic and repetitive sequence signatures. Moreover, the fixed and well-defined structure of the membrane-bound K segments suggests that dehydrins have the molecular prerequisites for higher level binding specificity and regulation, raising new questions about the complexity of their biological function.

The disordered plant dehydrin Lti30 protects the membrane during water-related stress by cross-linking lipids

“…In comparison, this value increased to 81 Ϯ 25% during portions of simulation trajectories in which the peptide was bound to the lipid headgroups. This supports previous experimental findings, where membrane binding was associated with formation of helical conformation of the K-segment (7).…”

“…Previous reports show that His-K-segments adopt a helical conformation upon binding the membrane and float over the membrane surface, with no visible oligomerization or aggregation (7). Here, we detected domain-entrapped diffusion for pH Յ7.4 but with large aggregates visible ( Fig.…”

“…Dehydrins are extremely hydrophilic and abundant in charged residues. Although there are several experimental reports on the involvement of K-segmentmembrane interactions (5)(6)(7), the molecular mechanism of how dehydrins perform cell-protective functions with their highly conserved sequences is still elusive. It has been reported for other intrinsically disordered proteins, e.g.…”

“…Literature suggests that the factors that influence the membrane binding of Lti30 include the protonation state of histidines flanking the K-segments, phosphor-ylation of Lti30 by protein kinase C on three sites within the K-segments and six sites in between the K-segments, and cleavage of Lti30 by proteases (6). Eriksson et al (7) reported in an NMR-based study that K-segments with flanking histidines undergo conformational changes from an unstructured protein to an amphipathic helix upon membrane binding and then float on the membrane outer leaflet. It was also hypothesized that Lti30 can form oligomers or can bind other biological targets that might be important for its function.…”

Folding of intrinsically disordered plant LEA proteins is driven by glycerol‐induced crowding and the presence of membranes

“…In the presence of glycerol, the presence of membranes, in particular ICMMs, induced additional folding of the LEA proteins investigated in this study. Binding of LEA proteins to membranes or the membrane‐mimicking detergent SDS associated with partial folding has been described previously for several dehydrins and other LEA proteins . In all these cases, electrostatic interactions are the driving‐force of protein binding.…”