Protein O-sulfonation
Post-translational O-sulfonation of a serine or threonine residue of proteins is detected, optionally comparatively, wherein the detected O-sulfonation is detected under a first physiological condition, and is compared with a control O-sulfonation detected under a second physiological condition, and a difference between the detected and control O-sulfonations indicates a difference between the first and second physiological conditions. Predetermined changes in physiological conditions are used to infer specific changes in O-sulfonation. Proteins are modified by introducing a predetermined change in O-sulfonation at a serine or threonine residue of the protein, and optionally, detecting a resultant change in O-sulfonation. These methods include introducing or increasing O-sulfonation, eliminating or reducing O-sulfonation; and derivatizing or substituting O-sulfonation.
1. A method of modifying an isolated endogenous protein expressed by a cell, said method comprising the steps of:
transforming the sulfoserine or sulfothreonine residue of the isolated endogenous protein into a lysine isostere that is aminoethylcysteine or beta-methylaminoethylcysteine, respectively, by a beta-elimination followed by Michael's addition, thereby modifying the isolated endogenous protein,
wherein the cell is cultured to produce the endogenous protein comprising the sulfoserine or sulfothreonine residue as a result of a post-translational modification in said cell,
wherein the endogenous protein is isolated from the cell,
and
wherein endogenous means the protein is expressed by the cell.
2. The method of claim 1 further comprising the subsequent step of:
selectively cleaving the endogenous protein or a peptide thereof comprising the lysine isostere with a lysine specific protease.
3. The method of claim 1 further comprising the prior step of:
identifying a serine or threonine residue of the endogenous protein as subject to O-sulfonation in the cell, wherein the serine or threonine residue becomes the sulfoserine or sulfothreonine residue through O-sulfonation.
4. The method of claim 1 further comprising the subsequent step of:
selectively cleaving the endogenous protein or a peptide thereof comprising the lysine isostere with a lysine specific protease; and the prior step of:
identifying a serine or threonine residue of the endogenous protein as subject to O-sulfonation in the cell, wherein the serine or threonine residue becomes the sulfoserine or sulfothreonine residue through O-sulfonation.