The Down-side Risk Associated with SWAP70 That Nobody Is Bringing Up

When MutM was reacted with either 8-oxoG��C or 8-oxoG��A, the addition of a 10-fold greater concentration of NExo or NApe did not increase the turnover of the substrate (Fig.?3A). The same result was also observed with Nth, where the addition of an excess of NExo or NApe did not increase the turnover of 5��-OHU or 8-oxoG��C (Fig.?3B). Furthermore addition of NApe or NExo to reactions containing MutM did not relieve the product inhibition observed with this glycosylase (not shown). Therefore, there was no biochemical evidence of cooperation between the bi-functional glycosylases and the 3�� processing http://www.selleckchem.com/products/Adriamycin.html enzymes. To further understand how Nth and MutM are integrated in meningococcal BER, we performed genetic analysis to determine the contribution of combinations of enzymes to bacterial survival under conditions of oxidative stress. We examined the effect of removing Nth and/or MutM in NApe-deficient bacteria. Removal of MutM from bacteria lacking NApe did not have any impact on survival, whereas the ��nape��nth double mutant demonstrated only 25% survival compared with the mutant lacking only NApe (Fig.?3C). This synergistic effect suggests that Nth, but not MutM, can compensate for NApe in the meningococcus. This probably occurs through the efficient lyase activity of Nth (Fig.?2), which can act on AP sites (Silhan et?al., 2011), participating in the strand incision of AP sites during BER, while the product inhibition observed with MutM fails to perform this function in vivo. Additionally, the effect of removing Nth and MutM from the ��nape��nexo double mutant was examined. The ��nape��nexo strain is more impaired for survival in the presence of oxidative stress than the single ��nexo deletion (Fig.?1), consistent with these enzymes having specialized functions within the cell. In this background, deletion of MutM (��nape��nexo��mutM) actually lead to a twofold increase in survival of the bacterium (Fig.?3D). This is consistent with MutM generating an increased burden of 3��-PO4 lesions, which reduces survival in the ��nape��nexo strain. There was also significant increase in bacterial survival following exposure to oxidative stress of the ��nape��nexo mutant following removal of both bi-functional glycosylases MutM and Nth with an increased recovery of 330% (P?