Product-assisted catalysis in base-excision DNA repair |
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Authors: | Fromme J Christopher Bruner Steven D Yang Wei Karplus Martin Verdine Gregory L |
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Institution: | Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA. |
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Abstract: | Most spontaneous damage to bases in DNA is corrected through the action of the base-excision DNA repair pathway. Base excision repair is initiated by DNA glycosylases, lesion-specific enzymes that intercept aberrant bases in DNA and catalyze their excision. How such proteins accomplish the feat of catalyzing no fewer than five sequential reaction steps using a single active site has been unknown. To help answer this, we report the structure of a trapped catalytic intermediate in DNA repair by human 8-oxoguanine DNA glycosylase. This structure and supporting biochemical results reveal that the enzyme sequesters the excised lesion base and exploits it as a cofactor to participate in catalysis. To our knowledge, the present example represents the first documented case of product-assisted catalysis in an enzyme-catalyzed reaction. |
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