Replication of phage φ29 DNAin vitro: role of the viral protein p6 in initiation and elongation

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Abstract
The φ29 protein p6 stimulates the formation of the protein p3–dAHP initiation complex when added to a minimal system containing the terminal protein p3, the φ29 DNA polyraerase p2 and φ29 DNA–protein p3 complex,by decreasing about 5 fold the Km value for dATP. In addition, protein p6 stimulates elongation of the p3–dAMP initiation complex. Whereas the effect of protein p6 on initiation is similar with protein p3–containing fragments from the right or left φ29 DNA ends, the stimulation of elongation is higher with the right than with the left φ29 DNA terminal fragment, suggesting DNA sequence specificity. The stimulation by protein p6 of the initiation and elongation steps of φ29 DNA replication does not require the presence of the parental protein p3 at the φ29 DNA ends. No effect of protein p6 was obtained on the elongation of the template-primer poly(dT)–(dA)12–18 by the φ29 DNA polymerase.