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. 1990 Sep;87(17):6555–6559. doi: 10.1073/pnas.87.17.6555

In vitro assembly of relaxosomes at the transfer origin of plasmid RP4.

W Pansegrau 1, D Balzer 1, V Kruft 1, R Lurz 1, E Lanka 1
PMCID: PMC54575  PMID: 2168553

Abstract

During initiation of conjugative transfer of DNA containing the transfer origin (oriT) of the promiscuous plasmid RP4, the proteins TraI, TraJ, and TraH interact and assemble a specialized nucleoprotein complex (the relaxosome) at oriT. The structure can be visualized on electron micrographs. Site- and strand-specific nicking at the transfer origin in vitro is dependent on the proteins TraI and TraJ and on Mg2+ ions. Substrate specificity is directed exclusively towards the cognate transfer origin: the RP4-specified TraJ protein cannot recognize the closely related oriT of plasmid R751. After nicking, TraI protein remains attached to the 5'-terminal 2'-deoxycytidyl residue at the nic site [Pansegrau, W., Ziegelin, G. & Lanka, E. (1990) J. Biol. Chem. 265, 10637-10644]. Nicking and relaxosome formation require supercoiled DNA. Thus, a complicated structure involving multiple plasmid-specified proteins and a defined region of DNA must be formed at the transfer origin to prepare the plasmid for generating the single strand to be transferred.

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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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