Figure 3.

Thin section images of proteinaceous-like “strings” that link transport vesicles to cisternal elements. (A) Coated vesicles with fibrous connections (arrows) connecting them to neighboring Golgi cisternae. The vesicle indicated by the arrowhead is attached simultaneously to two adjoining cisternae. (B) A coated vesicle is linked to a cisterna by two apparently flexible fibers (arrows) in the same plane of section. (C) A group of coated vesicles showing various filamentous extensions (arrows) making vesicle–vesicle or vesicle–cisterna connections. In grazing section, this cisternal element is seen to have linear features on its surface (indicated by arrowheads) that could correspond to portions of the filaments that link vesicles to cisternae. (D) A cisternal tip with a free coated vesicle linked to the tip by two filaments (arrows). (E) A partially coated Golgi vesicle tethered with two connections to a single cisternal membrane (arrows). (F) An uncoated vesicle attached by at least four fibers (arrows) to at least two distinct cisternal elements. (A–D) Golgi incubated with cytosol and ATP in the presence of GTPγS. (E and F) Golgi incubated with cytosol and ATP without GTPγS. Comparable fibrous attachments connecting vesicles to each other and to cisternae also can be observed in suitable thin sections of Golgi stacks of animal and plant cells but are more difficult to demonstrate because of the high electron density of cytoplasmic matrix, which is absent in cell-free preparations. (Magnifications: A, ×123,000; B, ×145,000; C and D, ×138,000; E and F, ×264,000; Bar = 100 nm.)