Protein labeling with cyanobenzothiazole conjugates
The invention provides compounds and methods for site-specifically labeling proteins with cyanobenzothiazole derivatives of formula I. For example, the invention provides methods for labeling the N-terminus of a protein that terminates with a cysteine residue. The invention also provides methods for isolating an N-terminally labeled protein and methods for detecting an N-terminally labeled protein.
1. A method for immobilizing a protein of interest, comprising:
a) contacting a sample comprising an N-terminal cysteine labeled protein of interest with a cyanobenzothiazole derivative of Formula I
wherein
Z is H, F, Cl, Br, I, CN, amino, alkylamino, dialkylamino, alkyl ester, carboxy, carboxylic acid salt, alkyl amide, phosphate, alkyl phosphonate, sulfate, alkyl sulfonate, nitro, or C 1 -C 10 alkyl optionally unsaturated and optionally substituted with amino, hydroxy, oxo (═O), nitro, thiol, or halo;
each R 1 is independently H, F, Cl, Br, I, CN, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, or C 1 -C 6 alkylthio, wherein each alkyl, alkoxy, or alkylthio is optionally substituted with F, Cl, Br, I, amino, alkenyl, alkynyl, cycloalkyl, aryl, alkyl sulfonate, or CO 2 M wherein M is H, an organic cation, or an inorganic cation;
n is 0, 1, or 2;
Y is a linking group comprising C 1 -C 16 alkylene optionally substituted with one or more halo, oxo (═O), C r O 6 alkyl, or C 1 -C 6 alkoxy, and optionally interrupted with one or more N(R 1 ), O, S, or —NH—C(═O)— groups; and
X is a solid support;
and
b) immobilizing the protein of interest.
2. The method of claim 1 , wherein the protein of interest is purified.
3. The method of claim 1 , wherein the solid support is a particle, resin, bead, or surface.
4. The method of claim 1 , wherein the solid support comprises a silicate, polymer, sepharose, cellulose, alginate, polystyrene, a membrane, or glass.
5. The method of claim 1 , wherein the solid support is paramagnetic or magnetic.
6. The method of claim 1 , wherein the protein of interest maintains its functionality upon immobilization.
7. The method of claim 1 , wherein immobilization provides site-specific immobilization of the protein of interest.
8. The method of claim 7 , wherein the site-specific immobilization occurs at the N-terminal cysteine of the protein of interest.