6-O-methyguanine containing damaged DNA DNA with no 6-O-methylated guanine MGMT/hAGT mediated DNA Damage Reversal Authored: Pegg, A, 2004-02-04 15:50:05 EC Number: 2.1.1.63 Edited: Joshi-Tope, G, 0000-00-00 00:00:00 GENE ONTOLOGYGO:0006307 Pubmed8434121 Reactive cellular catabolites can cause DNA damage by 6-O-methylation of guanine. 6-O-methylguanine can pair ambiguously with both C and T, and can cause transition mutations. Active reversal of such damage can be facilitated by proteins having 6-O-methylguanine-DNA methyltransferase (MGMT) activity.<p> MGMT removes the methyl group from the guanine and transfers it to the cysteine residue at position 145 on the protein itself. MGMT thus methylated is not regenerated, as the S-methylcysteine is very stable. This is an energetically expensive approach to DNA repair as one entire protein molecule is sacrificed per lesion that is corrected in this manner (Yang et al. 2011). Reactome Database ID Release 4373892 Reactome, http://www.reactome.org ReactomeREACT_1876