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Mutations in the ribonuclease H active site of HIV-RT reveal a role for this site in stabilizing enzyme-primer-template binding 总被引:2,自引:0,他引:2
The RNase H activity of HIV-RT is coordinated by a catalytic triad (E478, D443, D498) of acidic residues that bind divalent cations. We examined the effect of RNase H deficient E(478)-->Q and D(549)-->N mutations that do not alter polymerase activity on binding of enzyme to various nucleic acid substrates. Binding of the mutant and wild-type enzymes to various nucleic acid substrates was examined by determining dissociation rate constants (k(off)) by titrating both Mg(2+) and salt concentrations. In agreement with the unaltered polymerase activity of the mutant, the k(off) values for the wild-type and mutant enzymes were essentially identical using DNA-DNA templates in the presence of 6 mM Mg(2+). However, with lower concentrations of Mg(2+) and in the absence of Mg(2+), although both enzymes dissociated more rapidly, the mutant enzymes dissociated several-fold more slowly than the wild type. This was also observed on RNA-DNA templates. These results indicate that alterations in residues essential for Mg(2+) binding have a pronounced positive effect on enzyme-template stability and that the negative residues in the RNase H region of the enzyme have a negative influence on binding in the absence of Mg(2+). In this regard RT is similar to other nucleic acid cleaving enzymes that show enhanced binding upon mutation of active site residues. 相似文献
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The P236L Delavirdine-Resistant Human Immunodeficiency Virus Type 1 Mutant Is Replication Defective and Demonstrates Alterations in both RNA 5′-End- and DNA 3′-End-Directed RNase H Activities
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Peter Gerondelis Richard H. Archer Chockalingam Palaniappan Richard C. Reichman Philip J. Fay Robert A. Bambara Lisa M. Demeter 《Journal of virology》1999,73(7):5803-5813
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Selection of mutations in the connection and RNase H domains of human immunodeficiency virus type 1 reverse transcriptase that increase resistance to 3'-azido-3'-dideoxythymidine 总被引:1,自引:0,他引:1
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Brehm JH Koontz D Meteer JD Pathak V Sluis-Cremer N Mellors JW 《Journal of virology》2007,81(15):7852-7859