Characterization of a plasmid from Streptomyces coelicolor A3(2)

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Abstract
Covalently closed circular DNA with a MW of 20 .times. 106 was identified in strains of S. coelicolor A3(2) of various fertility types. Hybridization studies and digestion by various restriction endonucleases indicated that the circular DNAs (pSH1) were identical regardless of the fertility type (UF, IF or NF) of the strain from which it was isolated. The pSH1 DNA was cleaved to many fragments of the endonucleases HincII, SmaI and SalI and to 3 or 4 fragments by BamHI and PstI. Plasmid pSH1 carries single sites for each of the 2 restriction enzymes, EcoRI and HindIII. These sites are 7.6 .times. 106 daltons apart. Attempts to isolate the fertility factor SCP1 as covalently closed circular DNA were unsuccessful. The biochemically isolated plasmic pSH1 is probably not identical to the genetically characterized fertility factor SCP1, which was identified in an autonomous state in IF-type strains and in an integrated state in NF-type strains.