Fig. 7. After internalization by flip, M-C6-NBD-PC is sorted to the
vacuole and must pass through the PVC. Based on analysis of membrane
trafficking mutants deficient in the steps shown in the figure, we determined
that M-C6-NBD-PC must pass through the PVC in order to gain access
to the lumen of the vacuole. The key result leading to this model is that
class E vps mutants, which are defective in vesicular transport from the PVC
to the vacuole, do not sort M-C6-NBD-PC to the vacuole. Two models
of how M-C6-NBD-PC might gain access to the lumen of organelles in
the vps pathway are illustrated — namely, internalization into the PVC
by either invagination of the PVC or by a PVC-localized flippase (see
Discussion for details).
