Aug 2026· Planta· Vol 264· 0 citations· 68 references
Medicine
TL;DR
Structural similarities within the linker domain of different ABCB-type proteins revealed structural similarities within the linker domain, including the presence of [R/K-X-S/T] and [R/K-X-X-S/T] motifs, which are potential phosphorylation sites for kinases of the AGCVIII superfamily, and a phosphorylation-based regulatory mechanism is proposed for ABCB alkaloid transporters.
Dear Editor , The detoxi fi cation of phytotoxic compounds is a prerequisite for plant survival. ATP-binding cassette family C (ABCC) transporters play a pivotal role in the export of toxic compounds into vacuoles, a critical step in detoxi fi cation 1 . Arabidopsis thaliana ABCC2 ( At ABCC2) is responsible for the ef fl ux of glutathione conjugates of pesticides, such as atrazine and metolachlor, into the vacuoles 2 – 5 . Additionally, At ABCC2 can export arsenic-phytochelatin conjugates into vacuoles, resulting in increased arsenic tolerance 6,7 . Despite its critical role in plant detoxi fi cation, the biochemical and structural mechanisms underlying the function of At ABCC2 remain incompletely understood. To address this gap, we present cryo-electron microscopy (cryo-EM) structures of At ABCC2 in four states: apo, substrate bound, closed, and dimeric. Structural analysis revealed a unique architecture, distinguished by the atypical localization of its transmembrane domain 0 (TMD0) domain. Moreover, biochemical studies revealed that the TMD0 domain is critical for coordinating transport channel closure. The molecular basis of atrazine export by At ABCC2 was also determined. Additionally, the plant-speci fi c dimerization of At ABCC2 was demonstrated to be mediated by TMD2 and nucleotide-binding domain 2 (NBD2) rather than by the TMD0 domain. Notably, we found that although dimeric At ABCC2 represented a physiological form, its dimerization resulted in reduced substrate export activity. These fi ndings provide new insights into the detoxi fi cation mechanism of At ABCC2 and highlight the potential for using ABCC transporters to develop herbicide-resistant crops. Full-length At
An evolutionarily ancient regulatory module is uncovered that shapes the molecular organization and function of IE KEAs, advancing the understanding of plastid ion and pH homeostasis and plastid ribosome integrity.
Tobias Wunder, L. Holzner, Nikolay Manavski et al.· bioRxiv· 0 citations
Solute carrier proteins (SLCs) are essential membrane protein transporters of small solutes. Among them, the SLC12 family is known to facilitate transport of ions. Members of the SLC12 family ensure cell homeostasis by co-transporting chloride alongside sodium and/or potassium across the plasma membrane. The majority of SLC12 proteins are well described, and a recent surge in structural studies facilitated by cryo-electron microscopy revealed molecular details of their function. These include multiple conformations of the transporters, covering a range of functional states and providing a window into the ion transport mechanism. Yet, only limited knowledge exists regarding their dimerization or higher order oligomerization and its role in regulation, despite SLC12 proteins consistently operating as dimers. In this review, we highlight the structural knowledgebase established in recent years and summarize the varying dimerization mechanisms. Altogether, it is becoming increasingly clear that large conformational changes in dimeric arrangements deserve attention, alongside other understudied areas like lipid interactions, nucleotide or N-terminal binding to the dimerization domains, and potential roles of the less described member SLC12A9.
Alexandra Náplavová, Poul Nissen, R. K. Flygaard· Journal of Structural Biolog...· 0 citations
Abstract Theanine, a non-protein amino acid predominantly found in tea (Camellia sinensis), is a primary contributor to the characteristic umami and sweet taste of tea infusion and is associated with numerous health benefits. The biosynthesis of its direct precursor, ethylamine, is catalyzed by the enzyme CsAlaDC. The evolutionary origin of this enzyme and the molecular basis for its functional divergence from the serine decarboxylase CsSDC, however, remain poorly understood. In this study, through comprehensive genome-wide identification, phylogenetic, structural, and domain analyses, we demonstrate that CsAlaDC originated from CsSDC via gene duplication followed by functional specialization. Phe106 and Gly168 were identified as indispensable residues governing CsAlaDC enzymatic activity in vitro and in vivo through functional validation. Crucially, we pinpointed two specific codon substitutions—TAC(Tyr112) to TTT(Phe106) and TGT(Cys174) to GGT(Gly168)—as key evolutionary mutations responsible for the functional shift from SDC to AlaDC activity. These findings elucidate the evolutionary trajectory of CsAlaDC and provide mechanistic insights into the molecular regulation of theanine biosynthesis in tea plants.
Hui Zhou, Peixian Bai, Yongxin Wang et al.· Horticulture Research· 0 citations
Computational modelling, subcellular localisation, and functional assays across the DUP240 gene family identify Ktd1 as the central effector of the Dup240 family in toxin defence and provide a mechanistic framework for understanding Dup240 regulation.
Hatwan Nadir, Alex Pembery, K. Laidlaw et al.· bioRxiv· 0 citations
Alternative oxidase (AOX) is cyanide insensitive terminal oxidase of plant mitochondrial electron transport chain serving as important bypass from classical cytochrome pathway for reduction in generation of reactive oxygen species (ROS) and for maintenance of redox homeostasis under diverse stress conditions. While many studies have emphasised on AOX structure in premature form, the mitochondria localised mature form which is biologically relevant for substrate interaction is not much explored. In the current study, we have performed comparative structural and molecular docking analysis of mature AOX isoforms from stress-sensitive Arabidopsis thaliana and extremophile Eutrema salsugineum to elucidate molecular determinants of ubiquinol binding and stress tolerance. Homology models of AOX isoforms were constructed and validated through SWISS-MODEL, GalaxyWEB, and Ramachandran plot. Docking of activators (pyruvate, glyoxylate, oxaloacetate, 2-oxoglutarate) and substrate (ubiquinol) revealed strong hydrophobic interactions, predominantly Pi-Pi alkyl bonds, within conserved catalytic domains. Among all isoforms, AtAOX1a and EsAOX1a exhibited highest binding affinities with ubiquinol. In-silico site-directed mutagenesis and molecular dynamics simulations demonstrated that substitution of conserved hydrophobic residues, Val184 in AtAOX1a and Val118 in EsAOX1a, with aspartic acid (V→D) did not alter structural stability but significantly disrupted ubiquinol-binding pocket and reduced binding affinity indicating conserved valine residues as hydrophobic anchors crucial for substrate stabilisation. The study underscores hydrophobic interactions as key determinant of AOX function proposing valine as potential site for in-vitro mutagenesis to modulate AOX-mediated stress responses. The findings serve as foundation for future experimental studies addressing AOX mediated stress responses and exploring strategies for improving plant stress tolerance.
Varsha Venugopalan, Rajesh Parsanathan, D. Challabathula et al.· Journal of Biomolecular Stru...· 0 citations
