Abstract
Bacteriophage Mu, a highly efficient transposon during its lytic cycle in Escherichia coli, is always associated with the host DNA1. In mature Mu particles, both ends of Mu are heterogeneous in length and sequence owing to the presence of host DNA2–6. The right end contains host sequences which vary between 500 and 3,200 base pairs (bp), while the left end heterogeneity was proposed7 to correspond to ∼50–100 bp. To understand the mechanism by which a small amount of host DNA at the left end is packaged along with Mu DNA, we have now determined the precise lengths of these host sequences. The minimum size of the host sequences attached to the left end of the mature bacteriophage Mu DNA is 56 bp; host sequences longer than 144 bp are rare. The host sequences do not show a continuum from 56 to 144 bp but are rather packaged in discrete blocks. The first such block is 56–61 bp, the second is 67–72 bp and so on. Thus, each block represents fragments covering a 5–6-bp range, with a space of 5 bp between each block. It seems that Mu DNA is being measured in units of helical turns for packaging.
Published Version
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