Expression vectors with modified ColE1 origin of replication for control of plasmid copy number

摘要

In an expression vector having a ColE1 replication system, the homology of the RNAI and RNAII of the ColE1 origin of replication to uncharged tRNAs is modified mutations in the coding region of the RNAI gene and corresponding mutations in the RNAII gene. The mutation results in one or more base exchanges in loop 1 and/or loop 2 and/or loop 3 of RNAI and RNAII. In methods using this vector for producing recombinant proteins, plasmid copy number is stably maintained. In methods for plasmid production, high plasmid copy numbers can be obtained.