(A) Sequence alignment showing the conserved histidines of GTase domains among 3 different members in Reoviridae family. The conserved histidines are highlighted by green boxes. (B) Superimposition of GTase domains of CPV TP, orthoreovirus λ2, and aquareovirus VP1. Molecules were aligned using Cα positions for residues in domains. The GTase domains of CPV, orthoreovirus, and aquareovirus are in sky blue, yellow, and red, respectively. The GTP and Mg2+ bound to CPV GTase site are colored in gray. Inset: zoom-in view of the boxed region. Side chains of K234, H208, and H217 of CPV, K190, H223, and H232 of orthoreovirus and K196, H229, and H238 of aquareovirus are shown.