THE COS REGION OF LACTOCOCCAL BACTERIOPHAGE-PHI-LC3

The nucleotide sequence of the DNA regions flanking the cohesive end site of the temperate lactococcal bacteriophage phi LC3 was determined. Four pairs of sequence repeats of 8 to 13 base-pairs in length were revealed close to the cohesive ends. These repeats possibly represent signal sequences involved in phage DNA maturation and packaging. The start of an open reading frame was localized only 42 nucleotides from the left end of the phi LC3 phage double-stranded region, implying that transcription probably proceeds across the cos site. Compilation of the characteristics of the DNA termini of bacteriophages with complementary cohesive DNA ends suggests that phages of Cram-negative bacteria generally carry 5'-protruding single-strands whereas those of Cram-positive hosts carry 3'-protruding ends.