Structure-Function Differences among Type I Restriction Endonucleases

A Symmetrical Model for the Domain Structure of Type I DNA Methyltransferases

Kneale (1994) J. Mol. Biol. 243, 1-5

The HsdS subunit is composed of repeated domains, and conserved sequences, which allows a prediction of the structure through a symmetrical model :

We have isolated a deletion mutant of R.EcoR124I which results in a new DNA specificity which is GAA(n7)TTC. This mutant is deleted for the entire last one-third of hsdS. Deletion mutants with a symmetrical DNA specificity can be constructed using this model:

 In the MTase(D50) deletion mutant the HsdS(D50) subunit can dimerise to produce a "normal" HsdS subunit. Since the remaining protein of the HsdS(D50) subunit is know to recognise the 5'-GAA-3' sequence of the EcoR124I recognition sequence it is not surprising that the mutant MTase recognises 5'-GAA(n7)TTC-3'.

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© University of Portsmouth
Author Dr Keith Firman,
Page last updated September 28, 2008