共查询到20条相似文献,搜索用时 15 毫秒
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Ason B Bertram JG Hingorani MM Beechem JM O'Donnell M Goodman MF Bloom LB 《The Journal of biological chemistry》2000,275(4):3006-3015
The gamma complex of the Escherichia coli DNA polymerase III holoenzyme assembles the beta sliding clamp onto DNA in an ATP hydrolysis-driven reaction. Interactions between gamma complex and primer/template DNA are investigated using fluorescence depolarization to measure binding of gamma complex to different DNA substrates under steady-state and presteady-state conditions. Surprisingly, gamma complex has a much higher affinity for single-stranded DNA (K(d) in the nM range) than for a primed template (K(d) in the microM range) under steady-state conditions. However, when examined on a millisecond time scale, we find that gamma complex initially binds very rapidly and with high affinity to primer/template DNA but is converted subsequently to a much lower affinity DNA binding state. Presteady-state data reveals an effective dissociation constant of 1.5 nM for the initial binding of gamma complex to DNA and a dissociation constant of 5.7 microM for the low affinity DNA binding state. Experiments using nonhydrolyzable ATPgammaS show that ATP binding converts gamma complex from a low affinity "inactive" to high affinity "active" DNA binding state while ATP hydrolysis has the reverse effect, thus allowing cycling between active and inactive DNA binding forms at steady-state. We propose that a DNA-triggered switch between active and inactive states of gamma complex provides a two-tiered mechanism enabling gamma complex to recognize primed template sites and load beta, while preventing gamma complex from competing with DNA polymerase III core for binding a newly loaded beta.DNA complex. 相似文献
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Najmudin S Coté ML Sun D Yohannan S Montano SP Gu J Georgiadis MM 《Journal of molecular biology》2000,296(2):613-632
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Structures of HIV-1 RT-DNA complexes before and after incorporation of the anti-AIDS drug tenofovir 总被引:3,自引:0,他引:3
Tuske S Sarafianos SG Clark AD Ding J Naeger LK White KL Miller MD Gibbs CS Boyer PL Clark P Wang G Gaffney BL Jones RA Jerina DM Hughes SH Arnold E 《Nature structural & molecular biology》2004,11(5):469-474
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