Figure 1.

NES-dependent export of a complex containing bPKI and fluorescent streptavidin. The nuclei of living HeLa cells were co-injected with bPKI proteins, rhodamine streptavidin (RHOD-STV), and a 70-kDa fluorescent dextran (FITC-DEXTRAN) to mark the injection site. The WT bPKI protein mediates export of rhodamine streptavidin from the nucleus to the cytoplasm (Upper). In contrast, the NES mutant bPKI protein fails to mediate nuclear export of rhodamine streptavidin (Lower). These data show that the biotin-modified PKI protein is fully active for export, and that streptavidin does not contain a cryptic NES.