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DNA restriction dependent on two recognition sites: activities of the Sfi I restriction–modification system in Escherichia coli by Denzil T. Bilcock; Stephen E. Halford is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

What is DNA restriction dependent on two recognition sites: activities of the Sfi I restriction–modification system in Escherichia coli about?

In contrast to many type II restriction enzymes, dimeric proteins that cleave DNA at individual recognition sites 4–6 bp long, the __Sfi__ I endonuclease is a tetrameric protein that binds to two copies of an elongated sequence before cutting the DNA at both sites. The mode of action of the __Sfi__ I endonuclease thus seems more appropriate for DNA rearrangements than for restriction. To elucidate its biological function, strains of __Escherichia coli__ expressing the __Sfi__ I restriction–modification system were transformed with plasmids carrying __Sfi__ I sites. The __Sfi__ I system often failed to restrict the survival of a plasmid with one __Sfi__ I site, but plasmids with two or more sites were restricted efficiently. Plasmids containing methylated __Sfi__ I sites were not restricted. No rearrangements of the plasmids carrying __Sfi__ I sites were detected among the transformants. Hence, provided the target DNA contains at least two recognition sites, __Sfi__ I displays all of the hallmarks of a restriction–modification system as opposed to a recombination system in __E. coli__ cells. The properties of the system __in vivo__ match those of the enzyme __in vitro__. For both re

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Author

Denzil T. Bilcock; Stephen E. Halford

Publisher

John Wiley and Sons; Wiley (Blackwell Publishing); Blackwell Publishing Inc.; Wiley (ISSN 0950-382X)

Published

1999

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)