Taq polymerase - what exonuclease activities?

Stephen Scharf sjscharf at netcom.com
Mon Feb 21 12:08:12 EST 1994

In article <1994Feb17.210214.26290 at emba.uvm.edu>, brianf at med.uvm.edu (Brian
Foley) wrote:

> P. Hirst (PHirst at massey.ac.nz) wrote:
> : I'm trying find out exactly what exonuclease activities Taq polymerase
> : has, and which polymerase it is/ or which it's derived from.  The
> : literature I've found so far is far from precise in its description, so
> : any information anyone has would be greatly appreciated.
> 	Taq polymerase is the Thermus aquaticus equivalent of the E. coli 
> polA gene product.  The T. aquaticus polA gene sequence is in Genbank, as 
> is the E. coli gene.
> 	I suspect that some companies have made deletions in the Taq polA 
> gene in order to supply a T. aquaticus equivalent of the Klenow fragment 
> of E. coli polymerase, but I am not certain about this.  I have heard
> people refer to this Taq as "KlenTaq", but I have not seen it published.

With regard to the first question, native Taq polymerase has a
5'->3'exonuclease activity, but it does not have a 3'->5' proofreading type
exo activity like E. coli Pol I. There is in fact a "Klenow-like"
equivalent of Taq polymerase available from PE, commonly referred to as
"Stoffel fragment", which has an N-terminal deletion of 289 amino acids and
has no intrinsic 5'->3' exo activity.
Hope this helps. 
Stephen Scharf
sjscharf at netcom.com
CompuServe 72070,750

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