Enzyme-pore constructs
The invention relates to constructs comprising a transmembrane protein pore subunit and a nucleic acid handling enzyme. The pore subunit is covalently attached to the enzyme such that both the subunit and enzyme retain their activity. The constructs can be used to generate transmembrane protein pores having a nucleic acid handling enzyme attached thereto. Such pores are particularly useful for sequencing nucleic acids. The enzyme handles the nucleic acid in such a way that the pore can detect its component nucleotides by stochastic sensing.
1. A construct comprising: an α-hemolysin pore subunit, having an amino acid sequence with at least 95% homology to SEQ ID NO: 2, and an exonuclease or a polymerase,
wherein the exonuclease or polymerase is attached to the pore subunit at a position corresponding to an amino acid position of SEQ ID NO: 2 selected from the group consisting of positions 1, 7 to 21, 31 to 34, 45 to 51, 63 to 66, 72, 92 to 97, 104 to 111, 124 to 136, 149 to 153, 160 to 164, 173 to 206, 210 to 213, 217, 218, 223 to 228, 236 to 242, 262 to 265, 272 to 274, 287 to 290 and 294, and wherein the pore subunit retains its ability to form an α-hemolysin pore; and
wherein the exonuclease, when attached to the pore subunit, retains its ability to cleave nucleic acids to form individual nucleotides; or the polymerase, when attached to the pore subunit, retains its ability to sequentially add nucleotides to a nucleic acid polymer.
2. The construct of claim 1 , wherein the exonuclease or polymerase is attached to the pore subunit at a position corresponding to an amino acid position of SEQ ID NO: 2 selected from the group consisting of positions 7 to 21, 45 to 51, and 294.
3. The construct of claim 2 , wherein the exonuclease or polymerase is attached to the pore subunit at a position corresponding to an amino acid position of SEQ ID NO: 2 selected from positions 45 to 51.
4. The construct of claim 2 , wherein the exonuclease or polymerase is attached to the pore subunit at a position corresponding to an amino acid position 294 of SEQ ID NO: 2.
5. The construct of claim 2 , wherein the exonuclease or polymerase is attached to the pore subunit through at least one linker.
6. The construct of claim 5 , wherein the linker is a peptide linker or a chemical linker.
7. The construct of claim 6 , wherein the chemical linker comprises a bismaleimide crosslinker.
8. The construct of claim 7 , wherein the bismaleimide crosslinker is 1,4-bis(maleimido)butane (BMB) or bis(maleimido)hexane.
9. The construct of claim 2 , wherein the polymerase is a DNA polymerase.
10. The construct of claim 1 , wherein an amino or carboxy terminal amino acid of the exonuclease or polymerase is attached to the pore subunit at a position corresponding to amino acid position 1 or 294 of SEQ ID No. 2.
11. The construct of claim 1 , wherein the amino acid sequence of SEQ ID NO: 2 comprises an introduction of a cysteine residue for covalent attachment of the exonuclease or polymerase to the pore subunit.
12. The construct of claim 1 , wherein the polymerase is a DNA polymerase.
13. The construct of claim 1 , wherein the pore subunit is capable of forming a α-hemolysin pore made up to 6, 7 or 8 subunits.
14. A modified alpha-hemolysin pore for sequencing nucleic acids comprising 7 subunits, wherein one of the subunits is a construct according to claim 1 .