The SPR2 C-terminal domain is structurally similar to the C-terminal domain from the mRNA 5’-decapping factor, Ge-1.

(A) Structure of the A.t. SPR2 C-terminal domain, colored as in Fig 3A, shown in cartoon format. (B) Structure of the Drosophila melanogaster Ge-1 C-terminal domain (colored wheat, shown in cartoon format (PDB accession code: 2VXG, Chain A [43]). (C) Structural alignment of the SPR2 C-terminal domain and the D.m. Ge-1 C-terminal domain from 2VXG [43], oriented as in A and B. Major differences in domain architecture are labeled in red. Labels denote SPR2 secondary structure elements unless otherwise noted. (D-E) Splayed view of the Ge-1 C-terminal domain core, highlighting the residues buried in the core, contributed from helices α1, α2, α5, and α7 (D), and helices α3, α4, α6, and α8 (E), which respectively constitute opposite regions of the domain. The side chains of core residues are shown in stick format. Inset zoom in D compares homologous hydrophobic core residues between SPR2 and Ge-1 in the α1-α2 region, aligned and colored as in C. (F) Electrostatic surface potential mapped on the Ge-1 C-terminal domain structure; top view oriented as in B, bottom view after a 180° rotation about the y-axis.