Identification of a Nidovirales Orf1a N7-guanine cap Methyltransferase signature-sequence as a genetic marker of large genome Tobaniviridae

François Ferron; Humberto Julio Debat; Etienne Decroly; Bruno Canard

We performed a structure-based alignment of this Orf1a MTase with the integration of several structurally-defined eukaryotic RNA-cap N7-guanine MTases (Fig. 3A) , of which Ecm1 can be considered as prototypic [36] . The conserved amino-acids in these new MTase set remain essentially the same: two glycines of the SAM binding site (G54 and 56 in WBV, G74-76 in Ecm1), a histidine (H117 in WBV, H144 in Ecm1) immediately followed by either F or Y. Glu175 is also very conserved, and in the Ecm1 structure, its homosteric counterpart Glu225 is positioned close to His144 and interacts also with the guanine base, strongly suggesting that this MTase is an N7-guanine MTase. The alignment allows to define 5 conserved motifs which are represented in Fig. 3B , and structurally aligned onto the vaccinia N7-guanine MTase structure D12 (PDB: 4KCB). author/funder. All rights reserved. No reuse allowed without permission.