1x9m | pdb_00001x9m
T7 DNA polymerase in complex with an N-2-acetylaminofluorene-adducted DNA
Structural highlights
Function[THIO_ECOLI] Participates in various redox reactions through the reversible oxidation of its active center dithiol to a disulfide and catalyzes dithiol-disulfide exchange reactions. [DPOL_BPT7] Replicates viral genomic DNA. Non-processive DNA polymerase that achieves processivity by binding to host thioredoxin (TrxA). This interaction increases the rate of dNTP incorporation to yield a processivity of approximately 800 nucleotides (nt) per binding event. Interacts with DNA helicase gp4 to coordinate nucleotide polymerization with unwinding of the DNA. The leading strand is synthesized continuously while synthesis of the lagging strand requires the synthesis of oligoribonucleotides by the primase domain of gp4.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe carcinogen 2-acetylaminofluorene forms two major DNA adducts: N-(2'-deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-AAF) and its deacetylated derivative, N-(2'-deoxyguanosin-8-yl)-2-aminofluorene (dG-AF). Although the dG-AAF and dG-AF adducts are distinguished only by the presence or absence of an acetyl group, they have profoundly different effects on DNA replication. dG-AAF poses a strong block to DNA synthesis and primarily induces frameshift mutations in bacteria, resulting in the loss of one or two nucleotides during replication past the lesion. dG-AF is less toxic and more easily bypassed by DNA polymerases, albeit with an increased frequency of misincorporation opposite the lesion, primarily resulting in G --> T transversions. We present three crystal structures of bacteriophage T7 DNA polymerase replication complexes, one with dG-AAF in the templating position and two others with dG-AF in the templating position. Our crystallographic data suggest why a dG-AAF adduct blocks replication more strongly than does a dG-AF adduct and provide a possible explanation for frameshift mutagenesis during replication bypass of a dG-AAF adduct. The dG-AAF nucleoside adopts a syn conformation that facilitates the intercalation of its fluorene ring into a hydrophobic pocket on the surface of the fingers subdomain and locks the fingers in an open, inactive conformation. In contrast, the dG-AF base at the templating position is not well defined by the electron density, consistent with weak binding to the polymerase and a possible interchange of this adduct between the syn and anti conformations. Crystal structures of 2-acetylaminofluorene and 2-aminofluorene in complex with T7 DNA polymerase reveal mechanisms of mutagenesis.,Dutta S, Li Y, Johnson D, Dzantiev L, Richardson CC, Romano LJ, Ellenberger T Proc Natl Acad Sci U S A. 2004 Nov 16;101(46):16186-91. Epub 2004 Nov 4. PMID:15528277[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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