Thermostable DNA polymerases having reduced discrimination against ribo-NTPs
First Claim
1. A recombinant thermostable DNA polymerase that is a mutant form of a naturally occurring thermostable DNA polymerase, wherein said naturally occurring thermostable DNA polymerase has an amino acid sequence comprising amino acid sequence motif SerGlnIleGluLeuArgXaa (SEQ ID NO:
- 2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
wherein said mutant form has been modified to contain an amino acid other than glutamic acid (Glu) at position 4 of said sequence motif; and
wherein said mutant form possesses reduced discrimination against incorporation of an unconventional nucleotide in comparison to said naturally occurring thermostable DNA polymerase.
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Abstract
Modified thermostable DNA polymerases having enhanced efficiency for incorporating unconventional nucleotides, such as ribonucleotides, into DNA products, are advantageous in many in vitro synthesis applications. Such enzymes are particularly useful for use in nucleic acid sequencing protocols and provide novel means for DNA sequence analysis. Genes encoding the modified enzymes and methods for their production and use offer cost and efficiency advantages for DNA sequencing.
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Citations
25 Claims
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1. A recombinant thermostable DNA polymerase that is a mutant form of a naturally occurring thermostable DNA polymerase, wherein said naturally occurring thermostable DNA polymerase has an amino acid sequence comprising amino acid sequence motif SerGlnIleGluLeuArgXaa (SEQ ID NO:
- 2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
wherein said mutant form has been modified to contain an amino acid other than glutamic acid (Glu) at position 4 of said sequence motif; and
wherein said mutant form possesses reduced discrimination against incorporation of an unconventional nucleotide in comparison to said naturally occurring thermostable DNA polymerase. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 18, 19, 20)
- 2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
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2. A nucleic acid sequence encoding a recombinant thermostable DNA polymerase that is a mutant form of a naturally occurring thermostable DNA polymerase, wherein said naturally occurring thermostable DNA polymerase has an amino acid sequence comprising amino acid sequence motif SerGlnIleGluLeuArgXaa (SEQ ID NO:
- 2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
wherein said mutant form has been modified to contain an amino acid other than glutamic acid (Glu) at position 4 of said sequence motif; and
wherein said mutant form possesses reduced discrimination against incorporation of an unconventional nucleotide in comparison to said naturally occurring thermostable DNA polymerase. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
- 2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
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21. A method for sequencing a nucleic acid target which method comprises the steps of:
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(a) providing an unconventional nucleotide and a corresponding conventional nucleotide in a DNA sequencing reaction, wherein said unconventional and corresponding conventional nucleotides are present in a ratio of less than about 1;
1, wherein said DNA sequencing reaction contains a recombinant thermostable DNA polymerase that is a mutant form of a naturally occurring thermostable DNA polymerase, wherein said naturally occurring thermostable DNA polymerase has an amino acid sequence comprising amino acid sequence motif SerGlnIleGluLeuArgXaa (SEQ ID NO;
2), wherein "Xaa" at position 7 of said sequence motif is a valine residue (Val) or an isoleucine residue (Ile);
wherein said mutant form has been modified to contain an amino acid other than glutamic acid (Glu) at position 4 of said sequence motif; and
wherein said mutant form possesses reduced discrimination against incorporation of an unconventional nucleotide in comparison to said naturally occurring thermostable DNA polymerase;(b) treating the reaction of step (a) under conditions for primer extension to provide primer extension products comprising said unconventional nucleotide; (c) treating the primer extension products of step (b) under conditions for hydrolyzing said primer extension products; (d) resolving reaction products from step (c); and (e) determining the sequence of the nucleic acid target. - View Dependent Claims (22, 23, 24)
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25. A kit for sequencing a nucleic acid comprising a thermostable DNA polymerase enzyme that comprises the amino acid sequence SerGlnIleXaaLeuArgXaa (SEQ ID NO:
- 1), wherein "Xaa" at position 4 of this sequence is any amino acid residue but not a glutamic acid residue (Glu) and "Xaa" at position 7 of this sequence is a valine residue (Val) or an isoleucine residue (Ile), and a mixture of conventional dNTPs and at least one unconventional nucleotide, wherein the ratio of said unconventional nucleotide to said corresponding conventional nucleotide is less than one.
Specification