Khairnar NP, Misra HS
DNA polymerase X from Deinococcus radiodurans implicated in bacterial tolerance to DNA damage is characterized as a short patch base excision repair polymerase. [JOURNAL ARTICLE]
Microbiology 2009 Jun 18.
Deinococcus radiodurans R1 genome encodes an X-family DNA repair polymerase homologous to eukaryotic DNA polymerase beta. The recombinant deinococcal polymerase X purified from transgenic E. coli showed deoxynucleotidyl transferase activity. Unlike Klenow fragment of E. coli, this enzyme showed a short patch DNA synthesis on heteropolymeric DNA substrate. Recombinant enzyme showed 5'dRP lyase activity and base excision repair function in vitro, with the help of externally supplied glycosylase and AP endonuclease functions. The polymerase X disruption mutant of Deinococcus radiodurans expressing 5'dRP lyase and truncated polymerase domain was comparatively less sensitive to gamma radiation than polX deletion mutant. Both category mutants showed higher sensitivity to hydrogen peroxide. The excision repair mutants of E. coli expressing this polymerase, showed the functional complementation to UV sensitivity. These results suggested the involvement of deinococcal polymerase X in DNA damage tolerance of Deinococcus radiodurans possibly by contributing in DNA double strand break repair and base excision repair. Further, the less effect of gamma radiation in mutant expressing 5'dRP lyase and truncated polymerase domain suggested the enigmatic role of its PHP domain in polymerase activity, as shown in its 3-D structure reported recently.
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