Active Site Components of ResT

ResT shares a common chemical mechanism with the tyrosine recombinases and the type IB topoisomerases. As noted in Fig. 2, part of the C-terminal domain of ResT can be aligned with the catalytic domains of these proteins. However, there is also a contribution from part of the N-terminal domain for activating catalysis by a "hairpin-binding module" that seems to pre-

distort the DNA between the scissile phosphates to activate DNA cleavage and to facilitate rapid hairpin formation after the cleavage step (Bankhead and Chaconas 2004). It is the interplay between these two different active site components that accounts for the unique reaction of telomere resolution. I will examine each active site component in turn.

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