Modified polymerases for improved incorporation of nucleotide analogues
The invention relates to modified polymerase enzymes which exhibit improved incorporation of nucleotide analogs bearing substituents at the 3′ position of the sugar moiety that are larger in size than the naturally occurring 3′ hydroxyl group. Also described are methods of using the polymerases to incorporate nucleotides into polynucleotides, particularly in the context of DNA sequencing.
1. An altered family B archaeal DNA polymerase, wherein the second amino acid of the motif A region is mutated to alanine (A); and the third amino acid of the motif A region is mutated to an amino acid selected from the group consisting of serine (S), alanine (A), glycine (G), and the amino acids having beta-branched side chains, whereby the altered family B archaeal DNA polymerase is capable of incorporating a 3′ O-azidomethyl-modified nucleotide.
2. The polymerase of claim 1 , wherein the polymerase is selected from the group consisting of a Vent polymerase, a 9° N polymerase, a Pfu polymerase and a JDF-3 polymerase.
3. The polymerase of claim 2 , wherein the polymerase is a Pfu polymerase comprising the following mutation: Y410A.
4. The polymerase of claim 2 , wherein the polymerase is a JDF-3 polymerase comprising the following mutation: Y409A.
5. The polymerase of claim 1 , which exhibits an increased rate of incorporation of the modified nucleotide, compared to a control polymerase selected from wild type polymerase and a variant thereof lacking exonuclease activity.
6. The polymerase of claim 5 , wherein the control polymerase is selected from wild type Pfu polymerase and a Pfu polymerase comprising the following mutation: A486Y.
7. The polymerase of claim 5 , wherein the control polymerase is selected from wild type JDF-3 polymerase and a JDF-3 polymerase comprising one of the following mutations: A485T, P410L or A485T/P410L.
8. The polymerase of claim 1 , wherein the third amino acid of the motif A region is mutated to serine (S), alanine (A) or glycine (G).
9. The polymerase of claim 1 , wherein the third amino acid of the motif A region is mutated to isoleucine (I), threonine (T), valine (V) or leucine (L).
10. The polymerase of claim 1 , further comprising an amino acid substitution mutation at the first amino acid of the motif A region selected from tyrosine (Y), phenylalanine (F), isoleucine (I), alanine (A), valine (V), glutamine (Q), cysteine (C) or serine (S).
11. The polymerase of claim 10 , wherein the motif A region has one of the following mutant amino acid sequences: YST, FAI, AAA, YAS, YAV, YGI, YSG, SGG, CST, IAL, CGG, SAL, SAA, CAA, YAA, QAS, VSS, VAG, VAV, FAV, AGI, YSS, AAT, FSS or VAL.
12. The polymerase of claim 11 , wherein the motif A region has the amino acid sequence YAV or YAS.
13. The polymerase of claim 12 , wherein the polymerase is a Pfu polymerase having one of the following triple mutations: L409Y/Y410A/P411V or L409Y/Y410A/P411S.
14. The polymerase of claim 12 , wherein the polymerase is a JDF-3 polymerase having one of the following triple mutations: L408Y/Y409A/P410V or L408Y/Y409A/P410S.
15. The polymerase of claim 1 , further comprising at least one amino acid substitution mutation in the motif B region, whereby the activity of the polymerase is enhanced.
16. The polymerase of claim 15 , wherein the substitution mutation in the motif B region is to the second amino acid.
17. The polymerase of claim 16 , wherein the substitution mutation is to an amino acid selected from the group consisting of L, F, I, S, V and C.
18. The polymerase of claim 17 , wherein the substitution mutation is to L.
19. The polymerase of claim 15 , wherein the motif B substitution mutations are to G at the first amino acid position and L at the third.
20. The polymerase of claim 15 , wherein the motif B substitution mutations are to N at the first amino acid position and Q at the third.
21. The polymerase of claim 15 , wherein the motif B region has one of the following mutant amino acid sequences: SKN, GRD, KHN, ISN and THH.