Modified type A DNA polymerases
The present invention provides improved DNA polymerases, in particular, type A DNA polymerases, that may be better suited for applications in recombinant DNA technologies. Among other things, the present invention provides modified DNA polymerases derived from directed evolution experiments designed to select mutations that confer advantageous phenotypes under conditions used in industrial or research applications.
1. A modified Taq DNA polymerase that:
(i) has an amino acid sequence that has at least 95% amino acid sequence identity with wild type Taq DNA polymerase set out in SEQ ID NO.:1, but includes a substitution relative to SEQ ID NO: 1 at a position corresponding to position 507 of SEQ ID NO.:1, which substitution is E507K; and
(ii) has polymerase activity in catalyzing DNA template-directed synthesis of a DNA polynucleotide, which activity has increased salt-tolerance relative to the wild type Taq DNA polymerase of SEQ ID NO.:1.
2. The modified Taq DNA polymerase of claim 1 , wherein the polymerase has improved ability relative to that of SEQ ID NO.: 1, when used in a PCR reaction, to amplify DNA fragments of 2 kilobases or more in length.
3. The modified Taq DNA polymerase of claim 1 , wherein the polymerase has increased heparin-binding affinity relative to that of SEQ ID NO.: 1.
4. The modified Taq DNA polymerase of claim 1 , wherein the amino acid percent identity is at least 96%.
5. The modified Taq DNA polymerase of claim 1 , wherein the amino acid percent identity is at least 97%.
6. The modified Taq DNA polymerase of claim 1 , wherein the amino acid percent identity is at least 98%.
7. A modified Taq DNA polymerase having the amino acid sequence of SEQ ID NO.:16 (E7S).