Fig. 4.

Comparison between GCRV VP1 and MRV λ2. (a) Ribbon diagram of VP1 with functional domains shown in different colors. (b) Superposition of VP1 (red) and MRV λ2 (green), with enlarged views of the flap and the GTase domains. The channel for nascent mRNA release is marked by a dotted blue circle. (c) A slab of the cryo-EM map of pentameric turret (transparent) superimposed with five copies of VP1 models shown as ribbons. The arrow points to a protruding β-hairpin (Leu47–Thr57). The inset shows the core and the position of the slab (pointed by the two arrows). (d) Schematic illustration of VP1 depicting putative conformational changes (arrows) associated with the transition from the open state to the closed state of the turret protein. The right inset shows the VP1 GTase domain density (pink) superimposed with its backbone model (green ribbon).