Active site substitutions delineate distinct classes of eubacterial flap endonuclease.

ABSTRACT: FENs (flap endonucleases) play essential roles in DNA replication, pivotally in the resolution of Okazaki fragments. In eubacteria, DNA PolI (polymerase I) contains a flap processing domain, the N-terminal 5'-->3' exonuclease. We present evidence of paralogous FEN-encoding genes present in many eubacteria. Two distinct classes of these independent FEN-encoding genes exist with four groups of eubacteria, being identified based on the number and type of FEN gene encoded. The respective proteins possess distinct motifs hallmarking their differentiation. Crucially, based on primary sequence and predicted secondary structural motifs, we reveal key differences at their active sites. These results are supported by biochemical characterization of two family members--ExoIX (exonuclease IX) from Esc

SUBMITTER: Allen LM 

PROVIDER: S-EPMC2650880 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature