The DNA replication machine of a gram-positive organism.
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 taudeltadelta' "clamp loader." PolC can assemble with taudeltadelta' to form a PolC.taudeltadelta' complex. After PolC.taudeltadelta' 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 of E. coli DNA polymerase III. We show here that the S. pyogenes DnaE polymerase also functions with the beta clamp.
Bruck
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Howard Hughes Medical Institute, The Rockefeller University, Laboratory of DNA Replication, New York, New York 10021, USA.
O'Donnell
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology; D005075:Biological Evolution; D004258:DNA Polymerase III / Q000502:physiology; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D020035:Holoenzymes / Q000502:physiology; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000502:physiology; D013297:Streptococcus pyogenes / Q000235:genetics*
D001426:Bacterial Proteins; C103076:DnaX protein, Bacteria; D020035:Holoenzymes; C040220:DNA polymerase C; C074904:DNA polymerase III, alpha subunit; C023140:DNA replicase; D009713:Nucleotidyltransferases; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase