The first transesterification reaction between the branch point site and the 5’ splice site is a __________ reaction.
ExplanationThe first transesterification reaction is triggered by the 2’-OH of the conserved A at the branch site. This group acts as a nucleophile to attack the phosphoryl group of the conserved G in the 5’ splice site. This is an SN2 reaction that proceeds through pentavalent phosphorus intermediate.
