The 3′-Terminal Nucleotide Sequences of Bacteriophage λ DNA

Analyses of radioactive oligonucleotides in endonuclease digests of 3'-terminally labeled lambda DNA revealed the 3' terminal sequence -GTTACG for the l strand and -ACCCGCG for the r strand. These sequences, together with those previously known for the 5' cohesive ends, provide a total of 25 known base-pairs in the vicinity of the termini. When the cohesive ends are paired, the sequence between the nicks can be bisected by a 2-fold rotational axis of symmetry. Five of the first eight base-pairs, on either side of the axis, are rotationally symmetric. This symmetry may be involved in the recognition of the site by an enzyme responsible for formation of the cohesive ends.