Figure 1

RCD1 structure and interactions. (A) Domain structure (WWE, PARP, and RST domains) of AtRCD1. (B) Sequence alignment of AtRCD1-RST with the most related RST domain from barley, soybean, and moss. α-helix positions in AtRCD1-RST are shown at the top. Top alignment: Conservation of residues with colouring in accordance with percentage identity (Jalview; darker blue is more conserved). Middle top alignment: Colouring in accordance with number of contacts (6 Å cut-off) to other structural elements (helix 1–4 or loop 1–2) in the AtRCD1-RST structure (PDB 5OAO). Dark green is three, green two, and light green one contact. The β₃-position of the α_L-β₄ loop motif is grey. Middle bottom alignment: Residue groups that are in contact in the AtRCD1-RST structure (PDB 5OAO;5N9Q) and appear to co-evolve in same colour. The β₃-position of the α_L-β₄ loop motif is grey, Gly555 in dark grey. Bottom alignment: Conserved residues that cannot be explained by fold conservation are highlighted. Conserved residues are red, while conservative substitutions are light red. (C) Left: TF-interactome of AtRCD1 from the STRING database. Names of TFs, which have been shown to bind the RST domain³⁰, are shown. Right: Expanded AtRCD1:TF interactome predicted based on the expanded SLiM [ED].{1,2}[^RK][YF].{1,4}[^RK][DE]([LIVMF]|.L). (D) Structure of the AtRCD1 RST domain (light grey; PDB 5OAO) in modelled complex with AtDREB2A(255–272) (dark grey; PDB 5OAP)²⁵. AtRCD1-RST key residues (R551, R560, I563) for AtDREB2A(255–272) binding and the α-helix stabilizing hydrophobic staple motif residues, F259 and L264, of AtDREB2A(255–272), are highlighted. (E) NMR solution structure of AtRCD1-RST (light grey; PDB 5N9Q) and models (light grey) of the barley, soybean, and moss RST domains generated using I-TASSER⁷⁰. Left: Superposition of structure and models with residues having three or two contacts to other structural elements in dark green sticks and green lines, respectively. Middle: Superposition of structure and models with conserved residues not explained by fold conservation shown as sticks. Fully conserved residues are red while positions with conservative substitutions are light red. Right: Structure of AtRCD1-RST (light grey; PDB 5N9Q) with same residue highlights as the superpositions (left and middle).