Figure 1.
Methionine proximity-activated imaging reporter (Met-PAIR) through live-cell chemical modification of endogenous proteins and proximity-ligation assay (PLA). (a) General description of the PAIR method for “turn-off” sensing (left, blue shaded box) or “turn-on” sensing (right, red shaded box). Gray rectangle: analyte that deactivates methionine residues (e.g., H2O2 for actin). Blue ball: analyte that activates methionine residues (e.g., Ca for calmodulin). Green ball: an antibody-detectable chemical handle (e.g., Oregon Green and biotin). (b) Structure of alkyne-functionalized oxaziridine (Ox4) for the methionine labeling. (c) Schematic illustration of PLA for a protein with a methionine residue functionalized by the oxaziridine and chemical handle (green ball). Dark yellow strands: connector oligonucleotides that can be amplified by polymerase when transformed to circular oligonucleotides by ligase.