2005: replication functions of the linear plasmid lp17 of B. burgdorferi

1: Mol Microbiol. 2005 Jul;57(1):132-142. Related Articles, Links


Mapping of essential replication functions of the linear plasmid lp17
of B. burgdorferi by targeted deletion walking.

Beaurepaire C, Chaconas G.

Department of Biochemistry and Molecular Biology and Department of
Microbiology and Infectious Diseases, University of Calgary, Calgary,
Alberta T2N 4N1, Canada.

Summary The genome of the Lyme disease pathogen Borrelia burgdorferi
strain B31 MI includes one linear chromosome, 10 circular and 12 linear
plasmids. Members of four paralogous gene families, revealed by genome
sequencing, have been suggested as replication/partition functions for
both the linear and circular plasmids. Some of these genes have been
experimentally shown to be essential for the replication of the B.
burgdorferi replicons that encode them. In this study, we located the
region essential for replication of lp17, the second smallest linear
plasmid in B. burgdorferi. We used a novel in vivo method, targeted
deletion walking, to systematically delete DNA from either the left or
right end of lp17. We report that the region essential for replication
of lp17 is 1.8 kb (bp 7946-9766) and contains only one intact open
reading frame (BBD14). Expression of BBD14 is required for the
replication, suggesting that it is the replication initiator for lp17.
The BBD14 protein is a member of paralogous family (PF) 62 and we
present the first experimental evidence for the role of a PF 62 member.
Adjacent non-coding sequences are also required, suggesting that the
origin lies at least partially outside the coding region. Surprisingly,
deletion of BBD21, the ParA orthologue (PF 32), had little effect upon
plasmid stability or incompatibility. Finally, data are presented
suggesting that lp17 replication occurs preferentially on a linear
rather than a circular DNA molecule.

PMID: 15948955 [PubMed - as supplied by publisher]

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