Figures & data
Figure 1 Transmission electron micrographs of endocytic invaginations in wild type, vps1Δ and Vps1 I649K expressing cells. Transmission electron micrographs of 40–60 nm ultrathin sections of high pressure frozen/freeze substituted whole yeast cells showing representative invaginations of the plasma membrane in cells expressing wild type vps1 (a), no vps1 (b) or expressing the I649K vps1 mutant (c). In wild type and vps1 deletion strains most invaginations vary in depth between 20–60 nm and they are never more than 100 nm. In the I649K mutant, many invaginations are in this normal range, but a significant number exceed 100 nm (c) and can be over 300 nm in depth.
Figure 2 Schematic model of Vps1 function in endocytosis. During endocytic invagination in wild type cells Vps1 arrives at the onset of invagination and remains at the site until scisson occurs. In the absence of Vps1, the amphiphysin heterodimer Rvs161/Rvs167 localizes less well to the site and many events appear to retract towards the plasma membrane and the invaginations fail to undergo scission. Invaginations are also less likely to be directed perpendicularly into the cell. However in the presence of a self assembly defective mutant, vps1 I649K, the intramolecular GTPase cannot be stimulated and elongated invaginations are observed. This suggests that the transition of Vps1 to the self assembled form is part of the mechanism involved in vesicle scission.
