Figure 3.

A model for the spliceosomal B^* complex active site showing juxtaposition of several important groups during catalysis. In the work of Koodathingal et al., a site-specific phosphorthioate at position U80 in the U6 snRNA was used to stall spliceosomes prior to exon ligation [24]. Smith et al. created an orthogonal yeast spliceosome by mutating the branch site (BS)-U2 duplex [36]. This figure originated from reference [36] and is used with permission.