Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Life Sciences
Quaternary Interactions And Supercoiling Modulate The Cooperative Dna Binding Of Agt, Manana Melikishvili, Michael G. Fried
Quaternary Interactions And Supercoiling Modulate The Cooperative Dna Binding Of Agt, Manana Melikishvili, Michael G. Fried
Center for Structural Biology Faculty Publications
Human O6-alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O6-alkylguanine and O4-alkylthymine adducts in single-stranded and duplex DNAs. The search for these lesions, through a vast excess of competing, unmodified genomic DNA, is a mechanistic challenge that may limit the repair rate in vivo. Here, we examine influences of DNA secondary structure and twist on protein–protein interactions in cooperative AGT complexes formed on lesion-free DNAs that model the unmodified parts of the genome. We used a new approach to resolve nearest neighbor (nn) and long-range (lr) components from the ensemble-average cooperativity, ωave. We found …
Lesion-Specific Dna-Binding And Repair Activities Of Human O⁶-Alkylguanine Dna Alkyltransferase, Manana Melikishvili, Michael G. Fried
Lesion-Specific Dna-Binding And Repair Activities Of Human O⁶-Alkylguanine Dna Alkyltransferase, Manana Melikishvili, Michael G. Fried
Center for Structural Biology Faculty Publications
Binding experiments with alkyl-transfer-active and -inactive mutants of human O6-alkylguanine DNA alkyltransferase (AGT) show that it forms an O6-methylguanine (6mG)-specific complex on duplex DNA that is distinct from non-specific assemblies previously studied. Specific complexes with duplex DNA have a 2:1 stoichiometry that is formed without accumulation of a 1:1 intermediate. This establishes a role for cooperative interactions in lesion binding. Similar specific complexes could not be detected with single-stranded DNA. The small difference between specific and non-specific binding affinities strongly limits the roles that specific binding can play in the lesion search process. Alkyl-transfer kinetics with …
Cooperative Cluster Formation, Dna Bending And Base-Flipping By O6-Alkylguanine-Dna Alkyltransferase, Ingrid Tessmer, Manana Melikishvili, Michael G. Fried
Cooperative Cluster Formation, Dna Bending And Base-Flipping By O6-Alkylguanine-Dna Alkyltransferase, Ingrid Tessmer, Manana Melikishvili, Michael G. Fried
Center for Structural Biology Faculty Publications
O6-Alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O6-alkylguanine and O4-alkylthymine adducts in DNA, protecting the genome and also contributing to the resistance of tumors to chemotherapeutic alkylating agents. AGT binds DNA cooperatively, and cooperative interactions are likely to be important in lesion search and repair. We examined morphologies of complexes on long, unmodified DNAs, using analytical ultracentrifugation and atomic force microscopy. AGT formed clusters of ≤11 proteins. Longer clusters, predicted by the McGhee–von Hippel model, were not seen even at high [protein]. Interestingly, torsional stress due to DNA unwinding has the potential to limit cluster size …