Figure 4. VP1-template interactions.
Identification of VP1 residues that engage (A) the 3′CS+ (UGUGACC) or (B) the 3′CS-(AAAAGCC). The relevant amino acids and nucleotides are labeled, and hydrogen bonds are indicated as red lines. Labeled residues are in the fingers subdomain, except for Arg186, Lys188, and Arg190, which are in the N-terminal domain. Both complexes are stabilized, in part, by stacking of the C1 and C2 bases on each other. The VP1/3′CS+ complex is further stabilized by the stacking of G4 and U5 bases on each other, the interaction of the U7 base with Phe416, and the interaction of the G6 base with Arg190 and Arg701. (C) Merged structures of the VP1 apoenzyme (pink) and the VP1/3′CS+ complex (green), showing a shift of a loop-sheet element in the fingers subdomain that accompanies RNA binding. Amino-acid residues and nucleotides are labeled, and hydrogen bonds are indicated as red lines.