[Complete primary structure of DNA from the transducing bacteriophage lambda plac5].

In studying molecular mechanisms of specialized transduction, primary structure of the junction between the E. coli gene lacI and the lambda phage locus Ea47 in transducing bacteriophage lambda plac5 has been established. Along with the lambda DNA and E. coli lac operon structures as well as with our earlier data on another phage-bacterial junction in lambda plac5, it lead to the complete sequence of lambda plac5 DNA, including the lac5 substitution, a wellknown segment of lambdoid cloning vehicles. The lambda plac5 DNA is shown to consist of 48645 b.p. distributed as follows: 19368 (lambda left arm) + 3924 (lac5 substitution) + 25353 (lambda right arm). The presence of the phage pbL promoter near to the right end of the lac5 insert is shown. The lacI gene distal end in lambda plac5 proved to be considerably more long-stretched than it used to be believed, coding for 224 C-terminal amino-acid residues of lac repressor. The recombination studied in this paper, similarly to the abnormal prophage excision, occurred near to a Chi-like structure, which is partly homologous to the chi+lacZ site present in lambda plac5. On the basis of the data obtained, a key role of the E. coli RecBC system and Chi sites in the formation of long-stretched deletions in the bacterial cell has been suggested.