X-ray structure and activities of an essential Mononegavirales L-protein domain

Paesen, Guido C.; Collet, Axelle; Sallamand, Corinne; Debart, Françoise; Vasseur, Jean-Jacques; Canard, Bruno; Decroly, Etienne; Grimes, Jonathan M.

In CR-VI þ , however, an open, solvent-exposed area is found where this pocket is normally located (Fig. 6a) . Moreover, GpppG-or m GpppG binding was not observed in co-crystallization or soaking experiments, suggesting that CR-VI þ has a weak affinity for G at best and that the cap is not required for substrate recognition. This is consistent with CR-VI þ binding capped and uncapped RNAs with similar strength and being able to 2 0 O-methylate uncapped RNAs (Fig. 2b) . Strong binding would also prevent translocation of G into SUB P for N7-methylation. Although a high-affinity capbinding site is clearly absent from CR-VI þ , the low-affinity nucleoside binding to NS P and the convenient location of this pocket relative to SUB P suggest it could provide space for G without forming strong interactions ( Supplementary Fig. 5) .