Delimitation of cohesive ends site ( cos) of Streptomyces temperate bacteriophage R4

Abstract

The cohesive ends site (cos) of actinophage R4 was delimitated by assaying the in vivo packaging activity of cosmid derivatives in Streptomyces lividans. A region of 66 bp from -30 to +36 from the center of cohesive ends was required for the basal level of packaging activity. Two additional regions outside the basal sequences from -39 to -31 and from +37 to +97 were necessary for the high level of activity, defined as the accessory sequences. Direct- or inverted-repeat sequences were found within the delimitated region, which might be involved in the recognition by the terminase of actinophage R4.