Figure 1. METTL16 is widely conserved across eukaryotes.

(A) Phylogenetic tree showing the presence and absence of a METTL16 ortholog in 33 eukaryotic species. Linear protein structures with globular domains identified from Alphafold2 models are shown on the right of the tree. Domains are colored by cluster: MTD domains in blue, MTD +VCR/KA-1 domains in green, and VCR/KA-1 domains in orange. Likely loop/disordered regions with low confidence predictions are shown as grey lines. (B) Distance matrix heatmap showing the pairwise TMscore of segmented domains from the Alphafold2 predictions of 29 METTL16 orthologs. The X-ray structures of human METTL16 MTD and VCR, and TUT1 KA-1 are included as positive controls. Domains are grouped into clusters (diagonal boxes) using the same color scheme as in (A). (C) Boxplot showing TMscores of segmented domains from Alphafold2 predictions of 28 METTL16 orthologs superimposed onto experimentally determined structures of human METTL16 MTD and VCR, and TUT1 KA-1. (D) Superimposition of the VCR/KA-1 domain of Arabidopsis FIO1 predicted by Alphafold2 onto the X-ray structure of the human METTL16 VCR.

Figure 1—figure supplement 1. Structural analysis of fungal METTL16 orthologs.

(A) Alphafold2 predicted structure of S. pombe MTL16, which cannot be segmented into separate MTD and VCR/KA-1-like domains using the PAE method. Alphafold2 predicts that the MTD and VCR/KA-1 subdomains are sandwiched together by hydrogen bonding of Arginine 258 (orange, hydrogen bonding shown as dashed red lines) with backbone carbonyl oxygens, to create the superdomain structure. (B) Multiple sequence alignment of the 8 fungal METTL16 orthologs, of which 7 cannot be segmented into separate MTD and VCR/KA-1-like domains using the PAE method. Arg258 is highly conserved in these 7 orthologs (orange), but not in Y. lipolytica, which is segmentable into two domains.