The DNA replication machine of a gram-positive organism

被引:77
作者
Bruck, I [1 ]
O'Donnell, M [1 ]
机构
[1] Rockefeller Univ, Lab DNA Replicat, Howard Hughes Med Inst, New York, NY 10021 USA
关键词
D O I
10.1074/jbc.M003565200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
This report outlines the protein requirements and subunit organization of the DNA replication apparatus of Streptococcus pyogenes, a Gram-positive organism. Five proteins coordinate their actions to achieve rapid and processive DNA synthesis. These proteins are: the PolC DNA polymerase, tau, delta, delta', and beta. S. pyogenes dnaX encodes only the full-length tau, unlike the Escherichia coli system in which dnaX encodes two proteins, tau and gamma. The S. pyogenes tau binds PolC, but the interaction is not as firm as the corresponding interaction in E. coli, underlying the inability to purify a PolC holoenzyme from Gram-positive cells. The tau also binds the delta and delta' subunits to form a tau delta delta' "clamp loader." PolC can assemble with tau delta delta' to form a PolC.tau delta delta' complex. After PolC.tau delta delta' clamps beta to a primed site, it extends DNA 700 nucleotides/second in a highly processive fashion. Gram-positive cells contain a second DNA polymerase, encoded by dnaE, that has homology to the E. coli alpha subunit off. coli DNA polymerase III. We show here that the S. pyogenes DnaE polymerase also functions with the beta clamp.
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页码:28971 / 28983
页数:13
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