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. 1987 Aug;169(8):3737–3742. doi: 10.1128/jb.169.8.3737-3742.1987

P1 plasmid replication: measurement of initiator protein concentration in vivo.

J A Swack, S K Pal, R J Mason, A L Abeles, D K Chattoraj
PMCID: PMC212459  PMID: 3611028

Abstract

To study the functions of the mini-P1 replication initiation protein RepA quantitatively, we have developed a method to measure RepA concentration by using immunoblotting. In vivo, there are about 20 RepA dimers per unit-copy plasmid DNA. RepA was deduced to be a dimer from gel filtration of the purified protein. Since there are 14 binding sites of the protein per replicon, the physiological concentration of the protein appears to be sufficiently low to be a rate-limiting factor for replication. Autoregulation is apparently responsible for the low protein level; at the physiological concentration of the protein, the repA promoter retains only 0.1% of its full activity as determined by gene fusions to lacZ. When the concentration is further decreased by a factor of 3 or increased by a factor of 40, replication is no longer detectable.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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