Porphyromonas gingivalis, as a “keystone pathogen”, highlights its ability to adapt to the harsh inflammatory conditions of the periodontal pocket. Because the environmental stress response is a major determinant of its virulence, it is our long-term goal to gain a comprehensive understanding of its survival strategy(s). DNA damage is a major consequence of oxidative stress. While more than 20 different oxidatively altered bases might be generated by this stress, 8-oxo-7,8-dihydroguanine (8-oxoG) is one of the most common product of DNA damage. Guanine is the most susceptible base to oxidation and forms mainly 8-oxoG due to its low redox potential. In prokaryotic cells the presence of 8-oxoG is mainly repaired by base excision repair (BER). A survey of the P. gingivalis genome indicate that an important component of the BER system is missing. Because the average G + C content of the genome of P. gingivalis is 49%, a mechanism(s) to prevent or repair lesions resulting from guanine oxidation is vital. There is a gap in our comprehensive knowledge on a mechanism(s) for the repair of oxidative stress-induced DNA damage in P. gingivalis. We have previously demonstrated that there is an accumulation of 8-oxoG in the chromosome of P. gingivalis exposed to H2O2-induced oxidative stress. Neither BER nor nucleotide excision repair (NER), as observed in other strains, appear to be involved in the repair of the 8-oxoG lesion in P. gingivalis. DNA affinity fractionation identified PG1037, a conserved hypothetical protein, among others, that were preferentially bound to the oligonucleotide fragment carrying the 8-oxo-G lesion. PG1037 is part of the uvrA-pg1037-pcrA operon in P. gingivalis which is known to be upregulated under H2O2- induced stress. The purified recombinant PG1037 protein, likely via a reducing function, has the ability to prevent Fenton chemistry-mediated DNA damage in vitro and, under oxidative stress conditions, reduced the cleavage of the 8-oxoG lesion by the E.coli foramidopyrimidine glycosylase (Fpg) enzyme. In silico analysis of PG1037 shows a protein that contains a zinc finger domain, two peroxidase homologous motifs and a cytidylate kinase domain. The goal of the proposal is to test the hypothesis that a novel P. gingivalis protein (PG1037) carrying peroxidase motifs and a zinc finger domain is involved in the repair of oxidatively damaged DNA. Our aims are to confirm the specific role of PG1037 in the removal of 8-oxoG from duplex DNA and to evaluate any interaction of PG1037 with other proteins in that process. The data will provide a major conceptual advance on the molecular bases for the repair of oxidative stress-induced DNA damage in P. gingivalis and could likely support a unique and effective DNA repair mechanism we propose to designate “base redox repair”. It will set the stage, in a future RO1 application, to address specific structure-function questions on the vital components and their corporation in maintaining genomic st...