Abstract
Plasmid pAM beta 1 from Enterococcus faecalis uses a unidirectional theta mode of replication. We show here that this replication (i) is dependent on a plasmid-encoded replication protein (Rep) but not on a DNA structure typical for origins of most Rep-dependent plasmids and (ii) is initiated by DNA polymerase I (PolI). pAM beta 1 minimal replicon shares no homology with highly conserved ColE1-type replicons, which use PolI for initiation but do not encode a Rep, or with ColE2 and ColE3 replicons, which require PolI for replication and encode a Rep. We propose that pAM beta 1 and a number of other naturally occurring and closely related plasmids from a distinct plasmid class.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Base Sequence
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Conserved Sequence
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DNA Polymerase I / metabolism
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DNA Primers
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DNA Replication*
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DNA, Bacterial / biosynthesis
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DNA-Binding Proteins / biosynthesis
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DNA-Binding Proteins / metabolism*
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Enterococcus faecalis / genetics*
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Escherichia coli Proteins*
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Gram-Positive Bacteria / genetics*
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Molecular Sequence Data
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Open Reading Frames
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Plasmids*
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Promoter Regions, Genetic
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Replicon*
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Repressor Proteins / biosynthesis
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Repressor Proteins / metabolism*
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Restriction Mapping
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Sequence Homology, Nucleic Acid
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Templates, Genetic
Substances
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DNA Primers
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DNA, Bacterial
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DNA-Binding Proteins
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Escherichia coli Proteins
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RepE protein, E coli
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Repressor Proteins
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DNA Polymerase I