Fig. 5.

Model of the mechanism of the telomere resolution reaction showing the predicted prehairpinning step before the first transesterification. The composite active site is represented by the large gray oval (catalytic residues) and the smaller, darker oval (hairpin binding module). The axis of symmetry is indicated by the dashed line bisecting the telomeric DNA substrate. Prehairpinning is predicted to result in the formation of two small non-base-paired hairpin turnarounds. Although the cis or trans nature of ResT catalysis is not yet determined, the reaction chemistry is depicted in cis by ResT monomers for simplicity.