kitchingman at mbcf.stjude.org kitchingman at mbcf.stjude.org
Thu Aug 17 08:39:05 EST 1995

In article <111604089wnr at genesys.demon.co.uk>, Duncan Clark <Duncan at genesys.demon.co.uk> writes:
> In article: <c601591-1508951026240001 at>  c601591 at mizzou1.missouri.edu (Don Haut) writes:
>> I was just wondering if anyone had any idea why Xcm-1 is not as
>> "re-ligate-able" as other enzymes.  The NEB catalog states that after a
>> five fold over digestion with Xcm-1, >20% of the DNA fragments can be
>> ligated and of these >95% can be recut.  Most of the other enzymes >95% of
>> the DNA fragments can be ligated and recut.  I have several ideas but I
>> was wondering if anyone knew what is really going on.
>> Just wondering.
> If you look at any palindromic RE that leaves a single base overhang you 
> will find that they all ligate poorly if at all. I don't know if it is
> the kinetics of the ligase or what - just a fact of RE's.
> Duncan
XcmI is one of the class of restriction enzymes that does not cut within its
recognition sequence.The recognition sequence is;


with the cut coming 5 base pairs downstream from the A, which will leave a
single base pair overhang.  Like Duncan says, these are harder to ligate, but
also in this case you can have any of the four bases at the overhang.  Wiesblum
put two XcmI sites into a vector such that when it was cleaved it left T at
both overhangs, hence a T vector.

Geoff Kitchingman> 

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