Cell surface biotinylation is a biochemical approach to covalently bind membrane-impermeable
biotin to the extracellular domain of membrane proteins, such as receptor tyrosine
kinases (RTKs). Subsequent to ligand incubation periods, activated biotinylated receptors
may internalize from the cell surface into early endosomes and then travel through
intracellular compartments to either recycle back to the membrane or degrade in lysosomes.
The biotin-labeled proteins may be detected through affi nity purifi cation with streptavidin
agarose resins. This chapter describes methods for cell surface biotinylation to assess
RTK traffi cking steps.
