TY  - JOUR
A1  - Lawyer, F C
A1  - Stoffel, S
A1  - Saiki, R K
A1  - Chang, S Y
A1  - Landre, P A
A1  - Abramson, R D
A1  - Gelfand, D H
T1  - High-level expression, purification, and enzymatic characterization of full-length Thermus aquaticus DNA polymerase and a truncated form deficient in 5' to 3' exonuclease activity.
Y1  - 1993/05/01 
JF  - Genome Research 
JO  - Genome Research 
SP  - 275 
EP  - 287 
DO  - 10.1101/gr.2.4.275 
VL  - 2 
IS  - 4 
UR  - http://genome.cshlp.org/content/2/4/275.abstract 
N2  - The Thermus aquaticus DNA polymerase I (Taq Pol I) gene was cloned into a plasmid expression vector that utilizes the strong bacteriophage lambda PL promoter. A truncated form of Taq Pol I was also constructed. The two constructs made it possible to compare the full-length 832-amino-acid Taq Pol I and a deletion derivative encoding a 544-amino-acid translation product, the Stoffel fragment. Upon heat induction, the 832-amino-acid construct produced 1-2% of total protein as Taq Pol I. The induced 544-amino-acid construct produced 3% of total protein as Stoffel fragment. Enzyme purification included cell lysis, heat treatment followed by Polymin P precipitation of nucleic acids, phenyl sepharose column chromatography, and heparin-Sepharose column chromatography. For full-length 94-kD Taq Pol I, yield was 3.26 x 10(7) units of activity from 165 grams wet weight cell paste. For the 61-kD Taq Pol I Stoffel fragment, the yield was 1.03 x 10(6) units of activity from 15.6 grams wet weight cell paste. The two enzymes have maximal activity at 75 degrees C to 80 degrees C, 2-4 mM MgCl2 and 10-55 mM KCl. The nature of the substrate determines the precise conditions for maximal enzyme activity. For both proteins, MgCl2 is the preferred cofactor compared to MnCl2, CoCl2, and NiCl2. The full-length Taq Pol I has an activity half-life of 9 min at 97.5 degrees C. The Stoffel fragment has a half-life of 21 min at 97.5 degrees C. Taq Pol I contains a polymerization-dependent 5' to 3' exonuclease activity whereas the Stoffel fragment, deleted for the 5' to 3' exonuclease domain, does not possess that activity. A comparison is made among thermostable DNA polymerases that have been characterized; specific activities of 292,000 units/mg for Taq Pol I and 369,000 units/mg for the Stoffel fragment are the highest reported. 
ER  -