Figure 7.
Model of VSV L de-novo initiation complex. The 3′ end of Le (red) gains access to the active site of L through a template tunnel and is stabilized by the interaction between the active site and its first 2 nt. The active site recognizes specifically the NTPi (ATP) and the second NTP (CTP) (blue) incorporated during initiation to create a double base pair between ATP, CTP and the UG nt at the 3′ end of Le, resulting in a stable initiation complex. RNA synthesis is initiated with formation of the first phosphodiester mediated by the divalent ion (yellow).