FIGURE 4.

Mutation of O-linked glycosylation sites results in rapid loss of SNAP-Tac and SNAP-Tac trunc from the cell surface. A, schematic of SNAP-Tac and SNAP-Tac trunc together with their Thr → Ala mutants. The numbering system reflects the amino acids from the mature Tac protein. B–E, HeLa cells were labeled for 30 min at 4 °C with BG-488 and either fixed directly or chased for 30 min at 37 °C before fixation. Representative images for SNAP-Tac (B), SNAP-Tac(T→A) (C), SNAP-Tac trunc (D), and SNAP-Tac trunc(T→A) (E) are shown. DAPI staining shows cell nuclei. Bars, 10 μm.