Crystal structure of Arabidopsis DWARF14‐LIKE2 (DLK2) reveals a distinct substrate binding pocket architecture

Abstract

In Arabidopsis thaliana, the Sigma factor B regulator RsbQ-like family of α/β hydrolases contains the strigolactone (SL) receptor DWARF14 (AtD14), the karrikin receptor KARRIKIN INSENSITIVE2 (AtKAI2), and DWARF14-LIKE2 (AtDLK2), a protein of unknown function. Despite very similar protein folds, AtD14 and AtKAI2 differ in size and architecture of their ligand binding pockets, influencing their substrate specificity. We present the 1.5 Å crystal structure of AtDLK2, revealing the smallest ligand binding pocket in the protein family, bordered by two unique glycine residues. We identified a gatekeeper residue in the protein's lid domain and present a pyrroloquinoline-dione compound that inhibits AtDLK2's enzymatic activity.

Karrikin signalling: impacts on plant development and abiotic stress tolerance

“…In Arabidopsis, DLK2 expression is subject to regulation by SMAX1 and SMXL2, rather than other SMXL members ( Wang et al , 2020 ). To date, no clear function for DLK2 has emerged, as Arabidopsis dlk2 mutants show no obvious change in phenotype, and DLK2 itself shows poor hydrolytic activity towards GR24, but nevertheless retains enzymatic activity as a hydrolase ( Waters et al , 2012 ; Végh et al , 2017 ; Bürger et al , 2022 ). Furthermore, DLK2 and closely related homologues seem to have lost the highly conserved residues present in KAI2 and D14 that are thought to form part of the interaction interface with MAX2 ( Bythell-Douglas et al , 2017 ; Xu et al , 2018 ), which makes it unlikely that DLK2 has a receptor function akin to that of KAI2 and D14.…”