A rolling-circle plasmid from Psychrobacter sp. TA144: Evidence for a novel Rep subfamily

In this paper we report the cloning and sequencing of two small plasmids, p TAUp and pTADw, from the Antarctic Gram-negative Psychrobacter sp strain TA 144. The observation that pTAUp contains a putative Rep-coding gene (Psyrep ) suggested that its duplication occurs via a rolling-circle replication me chanism. This hypothesis was confirmed by the identification of the pTAUp s ingle-stranded DNA form. The putative pTAUp plus origin of replication was found at the 3' end of the Psyrep by using an in vivo complementation assay . Structural similarities at the level of (i) gene organization, (ii) prote in sequence, and (iii) nick site sequences strongly suggest that the psychr ophilic enzyme belongs to a new subfamily of replication enzymes, (C) 2000 Academic Press.