Restriction of lambda trp bacteriophages by Escherichia coli K |
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Authors: | W J Brammar N E Murray S Winton |
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Institution: | Department of Molecular Biology and Medical Research Council Molecular Genetics Unit, University of Edinburgh King''s Buildings, Edinburgh EH9 3JR, Scotland |
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Abstract: | trp-transducing derivatives of phage λ have been used to study Escherichia coli K specific restriction in vivo. The expression of the trp genes from unmodified phages during infection of a rec+, restricting host is eliminated by restriction. In a K-restricting recB,C host, where degradation of restricted phage DNA is prevented, expression of the trp genes is little affected by the presence of a single unmodified, K-restriction recognition site, even when that site is within the trpE gene. RI restriction, in contrast to K restriction, prevents trp gene expression in a recB,C host when the restriction target is between the trp genes and the relevant promoter. The presence of two K-restriction recognition sites in a λtrp phage can have a marked effect on trp gene expression. This effect can be interpreted as the result of preferential breakage between the two restriction recognition sites. We conclude that K restriction does not break susceptible DNA at, or even preferentially near, a restriction recognition sequence. |
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