Nanopore protein conjugates for detection and analysis of analytes
Provided are methods, compositions, and systems for the detection of a target analyte. Also provided are methods, compositions, and systems for determining the concentration one or more target analytes in fluid solution. The compositions include nanopore conjugates in which a nanopore protein monomer is joined to a capture tag. Tethered to the nanopore protein conjugate is an analyte ligand directed to a specific analyte. When a voltage is applied across a nanopore assembly including the nanopore conjugate, the nanopore captures the capture tag at a given capture rate. In the presence of the analyte to the analyte ligand, however, the capture rate of the capture tag changes, thus permitting detection of the analyte by the nanopore assembly. Further, based on the capture rate associated with binding between the analyte and the analyte ligand, the concentration of the analyte can be determined using association/dissociation kinetics.
1 . A nanopore protein conjugate comprising a nanopore protein monomer, an analyte attachment domain, and a capture tag, wherein (i) the capture tag comprises an amino acid sequence having at least 95% sequence identity to the amino acid sequence set forth as SEQ ID NO: 8, wherein (ii) the nanopore protein monomer of the nanopore protein conjugate comprises an amino acid sequence having at least 95% sequence identity to the sequence set forth as SEQ ID NO: 16 or SEQ ID NO: 6, and wherein (iii) the analyte attachment domain comprises an amino acid sequence that is located between the nanopore monomer and the capture tag.
2 . The nanopore protein conjugate of claim 1 , wherein the capture tag comprises an amino acid sequence having at least 98% sequence identity to the sequence set forth as SEQ ID NO: 8.
3 . The nanopore protein conjugate of claim 1 , wherein the nanopore protein monomer of the nanopore protein conjugate comprises an amino acid sequence having at least 98% sequence identity to the sequence set forth as SEQ ID NO: 16 or at least 98% sequence identity to the sequence set forth as SEQ ID NO: 6.
4 . The nanopore protein conjugate of claim 1 , wherein the nanopore protein conjugate comprises an amino acid sequence having at least 95% sequence identity to the sequence set forth as SEQ ID NO: 4 or SEQ ID NO: 7.
5 . An analyte detection complex, wherein the analyte detection complex comprises a nanopore protein conjugate of claim 1 and an analyte ligand that is joined to the nanopore protein conjugate, wherein the analyte ligand comprises a polypeptide sequence and wherein the analyte ligand is capable of binding a target analyte.
6 . The analyte detection complex of claim 5 , wherein the analyte ligand comprises an antibody or functional fragment thereof.
7 . The analyte detection complex of claim 5 , wherein the analyte ligand is joined to the nanopore protein conjugate via an isopeptide linkage.
8 . The analyte detection complex of claim 5 , wherein the analyte detection complex further comprises a linker member amino acid sequence and an attachment member amino acid sequence, wherein the linker member amino acid sequence attaches the analyte ligand to the attachment member amino acid sequence, wherein the attachment member amino acid sequence is joined to the nanopore protein complex at the analyte attachment domain of the nanopore protein conjugate, and wherein the linker member amino acid sequence and the attachment member amino acid sequence comprise a SpyCatcher/SpyTag binding pair of amino acid sequences, with the SpyTag sequence having at least 85% sequence identity to the amino acid sequence set forth as SEQ ID NO: 11.
9 . A nanopore assembly comprising at least one analyte detection complex of claim 5 .
10 . The nanopore assembly of claim 9 , wherein the nanopore assembly is a heptameric nanopore assembly and wherein each monomer of the heptameric nanopore assembly comprises an alpha-hemolysin monomer.
11 . A system for determining the concentration of analyte in a fluid solution, comprising:
a chip comprising a nanopore assembly, wherein the nanopore assembly is disposed within a membrane of the chip and wherein at least one nanopore protein monomer of the nanopore assembly comprises a capture tag and an analyte ligand, wherein the analyte ligand comprises a polypeptide sequence and wherein the analyte ligand is capable of binding a target analyte;
a sensing electrode positioned adjacent to or in proximity to the membrane, wherein the sensing electrode is configured to detect a signal from the nanopore assembly; and,
a computer processor, wherein the computer processor and sensing electrodes are configured to identify a first transition and a second transition associated with the nanopore assembly, the first transition corresponding to binding of the target analyte to the analyte ligand and the second transition corresponding to dissociation of the target analyte from the analyte ligand,
wherein the capture tag comprises an amino acid sequence having at least 95% sequence identity to the amino acid sequence set forth as SEQ ID NO: 8 and wherein the nanopore protein monomer comprises an amino acid sequence having at least 95% sequence identity to the sequence set forth as SEQ ID NO: 16 or SEQ ID NO: 6.
12 . The system of claim 11 , wherein a concentration of the target analyte in the fluid solution is determined based at least in part on the identified first transition and the identified second transition.
13 . The system of claim 11 , wherein the nanopore protein monomer is an alpha-hemolysin monomer.
14 . The system of claim 11 , wherein the nanopore protein conjugate comprises an amino acid sequence having at least 95% sequence identity to the sequence set forth as SEQ ID NO: 4 or SEQ ID NO: 7.
15 . The system of claim 11 , wherein the capture tag comprises an amino acid sequence having at least 98% sequence identity to the sequence set forth as SEQ ID NO: 8.