论文部分内容阅读
To efficiently remove a few damaged bases from the context of the entire genome,the DNA base repair proteins rely on remarkably specific detection mechanisms to locate base lesions.This efficient molecular recognition event inside cells has been extensively studied with various structural and biochemical tools.We have discovered a very unique base-flipping mechanism used by the DNA repair AlkB protein.This protein distorts DNA and favors ssDNA substrates over dsDNA ones.Potentially,it locates base lesions in dsDNA by imposing a constraint that targets less rigid regions of the duplex DNA.[1] These studies suggest that DNA base damage can be located by repair proteins using two mechanisms: a repair protein can probe and detect a weakened base pair resulting from mutagenic or cytotoxic base damage; alternatively,a protein can passively capture and stabilize an extrahelical base lesion.[2-3] To further understand the mechanism of methylated bases damage recognition by ABH2,for the first time,we have solved the complex structure of this protein bound to normal dsDNA sequences by using disulphide cross-linking strategy.This structural observation was supported by further base-opening dynamics study by fluorescence technique.Taken together,our chemical and structural studies on the direct DNA repair protein ABH2 suggest that AlkB family proteins actively search for weakened base pairs in their first step of damage searching.