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标题：A peptide switch regulates DNA polymerase processivity
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作者：Francisco J. López de Saro ; Roxana E. Georgescu ; Mike O'Donnell 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2003
卷号：100
期号：25
页码：14689-14694
DOI：10.1073/pnas.2435454100
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Chromosomal DNA polymerases are tethered to DNA by a circular sliding clamp for high processivity. However, lagging strand synthesis requires the polymerase to rapidly dissociate on finishing each Okazaki fragment. The Escherichia coli replicase contains a subunit ({tau}) that promotes separation of polymerase from its clamp on finishing DNA segments. This report reveals the mechanism of this process. We find that {tau} binds the C-terminal residues of the DNA polymerase. Surprisingly, this same C-terminal "tail" of the polymerase interacts with the {beta} clamp, and {tau} competes with {beta} for this sequence. Moreover, {tau} acts as a DNA sensor. On binding primed DNA, {tau} releases the polymerase tail, allowing polymerase to bind {beta} for processive synthesis. But on sensing the DNA is complete (duplex), {tau} sequesters the polymerase tail from {beta