[Structural changes in the composition of amplifying sequence AUD-Sr1 of Streptomyces rimosus after cloning into...

The presence of four EcoRV sites in the composition of the amplifying sequence AUD-Sr1 of S. rimosus resulting from its introduction on vector pUC19 into E. coli was studied. It was shown that the sequence had no EcoRV sites in a S. lividans strain while a number of plasmid and phage DNAs and chromosomal DNA of the strain were to be affected by EcoRV. The following regularities were observed: practically all the investigated hybrid plasmids from E. coli contained EcoRV sites in the composition of the AUD, EcoRV sites were present in strictly specified loci of the AUD sequence, appearance of an EcoRV site was accompanied by an increase in the size of the AUD fragment which contained it, the inserts detected in the SacI-PvuII fragment of the AUD were small in size (0.1 to 0.8 kb) and varied in different hybrid plasmids. The following mechanisms are discussed: insertion of the E. coli IS element into the AUD-Sr1 and high mutability of the amplifying sequence AUD-Sr1 in E. coli.