Proximity Histidine Labeling by Umpolung Strategy Using Singlet Oxygen
Keita Nakane, Shinichi Sato, Tatsuya Niwa, Michihiko Tsushima, Shusuke Tomoshige, Hideki Taguchi, Minoru Ishikawa, Hiroyuki Nakamura
Abstract
While electrophilic reagents for histidine labeling have been developed, we report an umpolung strategy for histidine functionalization. A nucleophilic small molecule, 1-methyl-4-arylurazole, selectively labeled histidine under singlet oxygen (1O2) generation conditions. Rapid histidine labeling can be applied for instant protein labeling. Utilizing the short diffusion distance of 1O2 and a technique to localize the 1O2 generator, a photocatalyst in close proximity to the ligand-binding site, we demonstrated antibody Fc-selective labeling on magnetic beads functionalized with a ruthenium photocatalyst and Fc ligand, ApA. Three histidine residues located around the ApA binding site were identified as labeling sites by liquid chromatography–mass spectrometry analysis. This result suggests that 1O2-mediated histidine labeling can be applied to a proximity labeling reaction on the nanometer scale.