Composite plasmids.

摘要

A composite plasmid selected from plasmid pMN1 having a molecular weight of 10.0 megadaltons, plasmid pMN2 having a molecular weight of 7.6 megadaltons, and plasmids pMN1 min and pMN2 min having a molecular weight of 11.3 megadaltons, said composite plasmid being formed by inserting plasmid pSL1 obtained from Streptomyces lavendulae into plasmid pCR1 obtained from Escherichia coli and having a kanamycin-resistant genetic marker and the following digestion characteristics to restriction enzymes: (i) pMN1 and pMN2 having one cleavage site to each of EcoRI and SalI and (ii) pMN1 min and pMN2 min having two cleavage sites to each of EcoRI and SalI. The composite plasmids have kanamycin-resistant genetic markers and hence transformant can be easily selected. The composite plasmids retain the DNA structure of actinomyces plasmid pSL1. In particular, composite plasmid pMN1 retains the greater part of the DNA structure of pSL1. The composite plasmids can effect DNA amplification in the presence of chloramphenicol.