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. 2024 Jun 4;15(7):e01035-24. doi: 10.1128/mbio.01035-24

Fig 6.

Alignment of amino acid sequences from HUH superfamily and conserved motifs one to three; structure of a mriyavirus HUH with spatial arrangement of the critical amino acid; HUH with active domain and another with an inserted loop are featured.

Sequence and structure conservation in the HUH endonucleases of mriyaviruses. (A) Alignment of the sequence segments of the HUH superfamily endonucleases containing the characteristic motifs I–III. The N-terminal motif I consists of hydrophobic residues, motif II consists of HUH (H: Histidine, U: hydrophobic residue), and C-terminal motif III (Yx2-3K; Y: tyrosine, x: any residue, K: lysine, blue). (B) A representative predicted structure of a mriyavirus HUH endonuclease superposed with the crystal structure of protein ORF119 from Sulfolobus islandicus rod-shaped virus 1 (green, pdb 2X3G-A, z-score 7.7). Yaravirus HUH endonuclease (MT293574_27) colored by plddt score. (C) Configuration of the catalytic amino acid residues of motifs II and III in the predicted structure of the mriyavirus HUH endonuclease (yaravirus MT293574_27, colored by plddt score). (D) Superposition of the structural models of the two HUH endonuclease domains of gamadviruses (short: KY346835_11 [green, aa 31–224, aa 1–30 unstructured, clipped off for representation], long: KY346835_10 [orange, aa 1353–1574 with additional inserted loop shown in purple, aa 104–1450])].