Strand switching of a replicative DNA helicase promoted by the E. coli primosome.
The E. coli primosome assembles at an origin on a single-stranded DNA, like that of phi X174, to promote replication of that template. Upon conversion to the duplex form, the primosome can generate a rolling circle product from this template. Rolling circle synthesis implies the transfer of the DnaB helicase from its initial loading site on the viral strand to a displaced complementary strand. Isolated primosomes promote only unit-length synthesis; supplementation with PriC, DnaC, and DnaT is necessary to reconstitute rolling circle synthesis. Rolling circle replication is sensitive to salts, whereas primosome assembly and unit-length synthesis are not. Thus, the primosome promotes two distinct reactions: assembly for first-round synthesis and strand switching for rolling circle synthesis.
Department of Biochemistry Beckman Center, Stanford University School of Medicine, California 94305.
G C
GC
Allen
N E
NE
Dixon
A
A
Kornberg
D000645:Ammonium Sulfate / Q000494:pharmacology; D001426:Bacterial Proteins; D010584:Bacteriophage phi X 174 / Q000378:metabolism; D002876:Chromosomes, Bacterial / Q000502:physiology; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D004277:DNA, Single-Stranded / Q000378:metabolism; D053488:DnaB Helicases; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008961:Models, Structural; D013997:Time Factors
D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004265:DNA Helicases; D053488:DnaB Helicases; D000645:Ammonium Sulfate