Unusual role of a cysteine residue in substrate binding and activity of human AP-endonuclease 1.

ABSTRACT: The mammalian AP-endonuclease (APE1) repairs apurinic/apyrimidinic (AP) sites and strand breaks with 3' blocks in the genome that are formed both endogenously and as intermediates during base excision repair. APE1 has an unrelated activity as a redox activator (and named Ref-1) for several trans-acting factors. In order to identify whether any of the seven cysteine residues in human APE1 affects its enzymatic function, we substituted these singly or multiply with serine. The repair activity is not affected in any of the mutants except those with C99S mutation. The Ser99-containing mutant lost affinity for DNA and its activity was inhibited by 10 mM Mg(2+). However, the Ser99 mutant has normal activity in 2 mM Mg(2+). Using crystallographic data and molecular dynamics simulation, we have pr

SUBMITTER: Mantha AK 

PROVIDER: S-EPMC2708089 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature