Method Tags Molecules' Neighbors

A reaction catalyzed by horseradish peroxidase (HRP) could help identify the molecules that come together to produce signal transduction, cell adhesion, and other biological events (Proc. Nat. Acad. Sci. USA, DOI:10.1073/pnas.0710346105). Such processes involve interactions among lipids and proteins that cluster together within cell membranes. A research group led by Koichi Honke of Kochi University Medical School, in Japan, found that HRP can convert an aryl azide-biotin reagent into an active radical species that can then label other molecules with biotin. The researchers exploited that reaction by tethering HRP to a molecule such as a membrane protein antibody, allowing the antibody to anchor to cell membrane targets, and then adding the reagent to biotinylate molecules surrounding the antibody's target. The group analyzed the resulting biotin-tagged molecules using antibody arrays to determine the components of the molecular cluster. The labeling technique can capture events in living cells, and it labels molecules out to a distance of about 300 nm from the target. The method is easy, allows for high throughput, and uses standard laboratory equipment, the authors note.