FIGURE 13-9 Post-translational translocation. This mechanism is fairly common in yeast and probably occurs occasionally in higher eukaryotes. Small arrows inside the translocon represent random sliding of the translocating polypeptide inward and outward. Successive binding of BiP·ATP to entering segments of the polypeptide prevents the chain from sliding out toward the cytosol. See K. E. Matlack et al., 1997, Science 277:938.