Probing the active site tightness of DNA polymerase in subangstrom increments.
نویسندگان
چکیده
We describe the use of a series of gradually expanded thymine nucleobase analogs in probing steric effects in DNA polymerase efficiency and fidelity. In these nonpolar compounds, the base size was increased incrementally over a 1.0-A range by use of variably sized atoms (H, F, Cl, Br, and I) to replace the oxygen molecules of thymine. Kinetics studies with DNA Pol I (Klenow fragment, exonuclease-deficient) in vitro showed that replication efficiency opposite adenine increased through the series, reaching a peak at the chlorinated compound. Efficiency then dropped markedly as a steric tightness limit was apparently reached. Importantly, fidelity also followed this trend, with the fidelity maximum at dichlorotoluene, the largest compound that fits without apparent repulsion. The fidelity at this point approached that of wild-type thymine. Surprisingly, the maximum fidelity and efficiency was found at a base pair size significantly larger than the natural size. Parallel bypass and mutagenesis experiments were then carried out in vivo with a bacterial assay for replication. The cellular results were virtually the same as those seen in solution. The results provide direct evidence for the importance of a tight steric fit on DNA replication fidelity. In addition, the results suggest that even high-fidelity replicative enzymes have more steric room than necessary, possibly to allow for an evolutionarily advantageous mutation rate.
منابع مشابه
Opposed Steric Constraints in Human DNA Polymerase and E. coli DNA Polymerase I
DNA polymerase selectivity is crucial for the survival of any living species, yet varies significantly among different DNA polymerases. Errors within DNA polymerase-catalyzed DNA synthesis result from the insertion of noncanonical nucleotides and extension of misaligned DNA substrates. The substrate binding characteristics among DNA polymerases are believed to vary in properties such as shape a...
متن کاملProbing the structure and function of the Escherichia coli DNA alkylation repair AlkB protein through chemical cross-linking.
Engineering chemical cross-linking groups at the protein/DNA interface provide a powerful method for probing the putative active site and a damage searching mechanism of the Escherichia coli alkylation DNA repair protein AlkB.
متن کاملA simplified protocol for producing Taq DNA polymerase in biology laboratory
Background: Taq DNA polymerase is a very important enzyme for molecular biological studies such as DNA amplification and DNA sequencing by the PCR. It is a standard enzyme that is used in 90% of molecular biology labs today. The aim of this study was to produce Taq DNA polymerase enzyme in E. coli by a reliable, practical, simple and low cost method. Materials and Methods: In this study, the T...
متن کاملExploring the effects of active site constraints on HIV-1 reverse transcriptase DNA polymerase fidelity.
To examine the concept of polymerase active site tightness as a criteria for DNA polymerase fidelity, we performed pre-steady-state single nucleotide incorporation kinetic analyses with sugar modified thymidine 5'-triphosphate (TTP) analogues and human immunodeficiency virus (HIV-1) reverse transcriptase (RT). The employed TTP analogues (T(R)TP) are modified at the 4'-position of the sugar moie...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 102 44 شماره
صفحات -
تاریخ انتشار 2005