The origin of transfer (oriT) of the conjugative plasmid R46: characterization by deletion analysis and DNA sequencing |
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Authors: | George M Coupland Anthony M C Brown and Neil S Willetts |
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Institution: | (1) Department of Molecular Biology, University of Edinburgh, King's Buildings, Mayfield Road, EH9 3JR Edinburgh, Scotland;(2) Present address: Institut für Genetik, Universität zu Köln, Weyertal 121, D-5000 Köln 41, Federal Republic of Germany;(3) Present address: Dept. of Microbiology and Immunology, University of California, 94143 San Francisco, CA, USA;(4) Present address: Biotechnology Australia Pty. Ltd., P.O.Box 20, 2069 Roseville, NSW, Australia |
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Abstract: | Summary The origin of transfer (oriT) is the sequence within which conjugal transfer of plasmid DNA is initiated, and is absolutely required in cis for plasmid mobilization. We have cloned oriT from the 52 kb IncN plasmid R46 on a 600 bp fragment, and mapped the limits of the relevant sequence by deletion analysis and transposon mutagenesis. The nucleotide sequence of the oriT region contains 13 direct repeats of an 11 bp consensus sequence, 3 different pairs of 10 bp inverted repeats, and a segment that is extremely A-T rich. The direct repeats are within a region required for high frequency transfer and their sequence is such that their periodic alignment along the helix may induce curvature of the DNA. Analysis of Tn1725 insertions within the sequenced fragment of R46 revealed that, unlike most other transposons, transposition of Tn1725 can cause target sequence duplications of three different sizes. |
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Keywords: | Bacterial conjugation oriT DNA sequence Tn1725 mutagenesis |
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