methyltransferase specificity

bafn6 at sussex.ac.uk bafn6 at sussex.ac.uk
Wed Mar 31 08:09:24 EST 1999

> maybe I'm missing something here, but the Rebase site is worth checking out
> regarding everything about restriction enzymes and methyltransferases. It can
> be found at:
> http://rebase.neb.com/rebase/rebase.html 
> Hope that helps.
> Markus
> bafn6 at sussex.ac.uk wrote:
> > I'm trying to establish whether a particular nucleotide sequence contains a
> > recognition sequence of a known methyltransferase (and one that will
> > methylate a particular base within that particular sequence). Is there an
> > efficient way of achieving this task? Anything online? I've been browsing
> > through the 1990 review in GENE but am not confident that I haven't missed
> > something.

I guess my original message wasn't too clear. Basically when I transform a
particular strain with a plasmid, one (out of many) HaeIII sites is not
cleaved. If this DNA is then retransformed back into E. coli that HaeIII
site becomes cleavable again. A likely explanation for this is that the
first cytosine in  that particular HaeIII site is methylated by the strain,
inhibiting the action of the RE. If there is a MTase around then it doesn't
recognise just the HaeIII site because the others aren't affected. I've
looked for REs that might recognise the region around that HaeIII site but
none of the others, but without luck.

Just curious as to what caused me some days of concern wondering why the
plasmid I got out was different to the one I put in.

Not sure if I want to chase this fellow up, but if anyone has some pointers
to quick and easy protocols for isolating RE / MTases then please pass them

Thanks again

Neil Crickmore
University of Sussex

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