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Structural Model of M.EcoR124I
 We have recently published a structural model for the DNA methylase of
the Type IC R-M enzyme EcoR124I. This work was based on two
X-ray crystallographic structures for the HsdS subunit (Calisto
et al., 2005;
Kim et al., 2005)
and a published pdb file for the structure of the HsdM subunit
of EcoKI (Obarska
et al., 2006), which allowed in
silico
modelling of the complete MTase based on the know EcoR124I DNA
sequence. In addition, information from van Noort et al (2004),
who had first visualised the EcoR124I endonuclease and MTase
bound to DNA, was used to direct the inclusion of "bent" DNA,
where the MTase was shown to introduce a bend of 49°
in the DNA. This can be seen in the animated gif above.
This model was then used to analyse a series of mutations that
had been isolated within the hsdS gene and allowed some
prediction of the "mechanism behind the phenotypes".
Structural Model of HsdR.GIF)
A combination of biophysical analysis and in silico
modelling has been applied to the HsdR subunits of Type I R-M systems (Obarska-Kosinska
et al 2008), following an earlier analysis of the
domain structure of the HsdR subunit of EcoKI (Dryden et
al., 1995) using limited proteolysis. Small angle neutron scattering
provided a "confining" space into which the modelled domains of HsdR were
fitted.
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