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Streptomyces linear plasmids that contain a phage‐like, centrally located, replication origin
Author(s) -
Chang PoaChun,
Kim EungSoo,
Cohen Stanley N.
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1996.01526.x
Subject(s) - plasmid , biology , replicon , origin of replication , genetics , dna , streptomyces , dna replication , temperateness , gene , bacteriophage , escherichia coli , bacteria
Unlike previously studied linear replicons containing 5′ DNA termini covalently bound to protein, pSLA2, a 17 kb linear plasmid of Streptomyces rochei , initiates replication internally rather than at the telomeres (Chang and Cohen, 1994). Here we identify and characterize the replication origin of pSLA2, showing that it contains a series of direct repeats (iterons) within a centrally located gene encoding an essential DNA‐binding protein (Rep1); a second essential protein (Rep2), which resembles prokaryotic DNA helicases and has ATPase activity stimulated by single‐stranded DNA, is expressed from the same transcript. A 430 bp locus separated by almost 2 kb from the iterons of the origin specifies an as yet undefined additional function required in cis for plasmid replication. pSCL, a 12 kb linear plasmid of Streptomyces clavuligerus , contains, near the centre of the plasmid, a region configured like the pSLA2 origin. The replication regions of pSLA2 and pSCL, which are capable of propagating plasmid DNA in either a circular or linear form (Shiffman and Cohen, 1992; Chang and Cohen, 1994) resemble those of temperate bacteriophages of the Enterobacteriacae and Bacillus . Our observations suggest that Streptomyces linear plasmids may occupy an evolutionarily intermediate position between circular plasmids and linear phage replicons.