Metabolic Labeling of Protein Antigens with [³⁵S]Methionine

Abstract

Metabolic labeling of antigens can be achieved by supplementation of the cell culture medium with radioactive amino acid precursors such as [³⁵S]methionine during the incubation period of target cells. In this protocol, intracellular unlabeled methionine levels are reduced by starvation of cells for 0.5–1 h before the addition of labeled [³⁵S]methionine and incubation for 0.5–4 h. Upon completion of the metabolic labeling process, cells can be prepared for immunoprecipitation by lysis or alternatively pelleted and frozen for cell lysate preparations at a later time.